Severe hepatitis cases in children are increasingly recognized, but the exact etiology remains unknown in a significant proportion of patients. Cases of indeterminate severe hepatitis (iSH) may progress to indeterminate pediatric acute liver failure (iPALF), so understanding its immunobiology is critical to preventing disease progression. Hemophagocytic lymphohistiocytosis (HLH) is a systemic hyperinflammatory disorder associated with T-cell and macrophage activation with liver injury.

We hypothesized that a high proportion of patients with iSH demonstrate systemic T-cell activation similar to HLH before developing iPALF and that the degree of T-cell activation in iSH might correlate with outcomes.

From 2019 to 2022, 14 patients with iSH and 7 patients with PALF of known, nonimmune etiology were prospectively enrolled. We compared immune signatures of iSH, HLH, known PALF, and healthy controls.

We found that patients with iSH have increased CD8+ T-cell activation and high IFN-γ activity similar to HLH. The amplitude of CD8+ T-cell activation was predictive of iSH progression to iPALF. We also found that in patients with iSH, ferritin had only modest elevation. However, the ratio of age-normalized plasma soluble IL-2 receptor to ferritin level can distinguish iSH from known PALF and HLH. As proof of concept, we report that in 3 patients with steroid-refractory iSH, emapalumab, an IFN-γ blocking antibody used in combination with steroids, improved liver function and may have prevented progression to PALF.

Flow-based T-cell activation markers could help in early identification and risk stratification for targeted intervention in patients with iSH.

Primary hemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory syndrome caused by inborn errors of cytotoxicity. Patients with biallelic PRF1 null mutations (encoding perforin) usually develop excessive immune cell activation, hypercytokinemia, and life-threatening immunopathology in the first 6 months of life, often without an apparent infectious trigger. In contrast, perforin-deficient (PKO) mice only develop HLH after systemic infection with lymphocytic choriomeningitis virus (LCMV). We hypothesized that restricted microbe-immune cell interactions due to specific pathogen-free (SPF) housing might explain the need for this specific viral trigger in PKO mice. To investigate the influence of a "wild" microbiome in PKO mice, we fostered PKO newborns with Wildling microbiota ('PKO-Wildlings') and monitored them for signs of HLH. PKO-Wildlings survived long-term without spontaneous disease. Also, systemic infection with vaccinia virus did not reach the threshold of immune activation required to trigger HLH in PKO-Wildlings. Interestingly, after infection with LCMV, PKO-Wildlings developed an altered HLH pattern. This included lower IFN-γ serum levels along with improved IFN-γ-driven anemia, but more elevated levels of IL-17 and increased liver inflammation compared with PKO-SPF mice. Thus, wild microbiota alone is not sufficient to trigger HLH in PKO mice, but host-microbe interactions shape inflammatory cytokine patterns, thereby influencing manifestations of HLH immunopathology.

Neonatal hemophagocytic lymphohistiocytosis (nHLH), defined as HLH that presents in the first month of life, is clinically devastating. There have been few large descriptive studies of nHLH.

The objective of this study was to perform a meta-analysis of published cases of nHLH.

A comprehensive literature database search was performed. Cases of HLH were eligible for inclusion if clinical analysis was performed at age ≤30 days. Up to 70 variables were extracted from each case.

A total of 544 studies were assessed for eligibility, and 205 cases of nHLH from 142 articles were included. The median age of symptom onset was day of life 3 (interquartile range [IQR]: 0-11, n = 141). Median age at diagnosis was day of life 15 (IQR: 6-27, n = 87). Causes of HLH included familial HLH (48%, n = 99/205), infection (26%, n = 53/205), unknown (17%, n = 35/205), macrophage activation syndrome/rheumatologic (2.9%, n = 4/205), primary immune deficiency (2.0%, n = 5/205), inborn errors of metabolism (2.4%, n = 5/205), and malignancy (2.0%, n = 4/205). Fever was absent in 19% (n = 28/147) of all neonates and 39% (n = 15/38) of preterm neonates. Bicytopenia was absent in 26% (n = 47/183) of patients. Central nervous system (CNS) manifestations were reported in 63% of cases (n = 64/102). Liver injury (68%, n = 91/134) and/or liver failure (24%, n = 32/134) were common. Flow cytometry was performed in 22% (n = 45/205) of cases. Many patients (63%, n = 121/193) died within the period of reporting. Discernable values for HLH diagnostic criteria were reported between 30% and 83% of the time.

Evaluation of nHLH requires rapid testing for a wide range of differential diagnoses. HLH diagnostic criteria such as fever and bicytopenia may not occur as frequently in the neonatal population as in older pediatric populations. Neurologic and hepatic manifestations frequently occur in the neonatal population. Current reports of nHLH suggest a high mortality rate. Future publications containing data on nHLH should improve reporting quality by reporting all clinically relevant data.

Hemophagocytic lymphohistiocytosis (HLH) patients who need intensive care usually have multiple organ failure and poor prognosis. However, the clinical characteristics, therapeutic efficacy and outcome in these critically ill HLH patients have remained unclear.

We performed a retrospective study of 50 critically ill HLH patients from September 2013 to October 2022. Patients' information was collected, and the overall survival rate was estimated.

Fifty HLH patients need intensive care, and the median sequential organ failure assessment (SOFA) score was 8. 66.00% patients had septic shock, 60.00% had disseminated intravascular coagulation (DIC) and 56.00% had acute respiratory distress syndrome (ARDS). 64.00% patients needed vasoactive drugs, 60.00% needed invasive or non-invasive positive pressure mechanical ventilation, and 12.00% needed continuous renal replacement therapy (CRRT). Among 18 patients received the etoposide-based regimens, the median time for 17 patients to remove ECG monitoring was 13 days (4-30 days); the median time to remove respiratory support in 10 patients was 8.5 days (4-21 days); the median time for 5 patient to convert from dominant DIC to non-dominant DIC was 4 days (1-14 days) and the median time for 6 patients to stop using vasoactive drugs was 10 days (2-14 days). After 4 weeks of treatment, 7 patients were evaluated as NR, 6 achieved PR, and 5 could not be evaluated. The ORR was 55.56%. Up to the last follow-up, the OS rate of patients receiving etoposide-based regimens was 66.67%. In contrast, all 32 HLH patients in other groups died. Univariate analysis showed that PCT > 0.5 ug/L, PT prolonged > 6 s, TBil > 25umol/L, respiratory failure, renal failure, liver failure and did not receive etoposide- based regimens were the negative factors affecting survival (P = 0.001, 0.017, 0.043, 0.001, 0.000, 0.029, 0.000).

HLH patients who need intensive care timely used etoposide-based HLH regimens might rescue critically ill patients successfully.

Epstein-Barr virus (EBV) is a ubiquitous and predominantly B cell tropic virus. One of the most common viruses to infect humans, EBV, is best known as the causative agent of infectious mononucleosis (IM). Although most people experience asymptomatic infection, EBV is a potent immune stimulus and as such it elicits robust proliferation and activation of the B-lymphocytes it infects as well as the immune cells that respond to infection. In certain individuals, such as those with inherited or acquired defects affecting the immune system, failure to properly control EBV leads to the accumulation of EBV-infected B cells and EBV-reactive immune cells, which together contribute to the development of often life-threatening cytokine storm syndromes (CSS). Here, we review the normal immune response to EBV and discuss several CSS associated with EBV, such as chronic active EBV infection, hemophagocytic lymphohistiocytosis, and post-transplant lymphoproliferative disorder. Given the critical role for cytokines in driving inflammation and contributing to disease pathogenesis, we also discuss how targeting specific cytokines provides a rational and potentially less toxic treatment for EBV-driven CSS.

The laboratory diagnosis of cytokine storm syndromes (CSSs), i.e., hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS), is often challenging. The laboratory features using routinely available tests lack specificity, whereas confirmatory testing is available in only few laboratories in the United States. The disease mechanisms are still largely unclear, particularly in adults. In this chapter, the pathogenesis of CSSs, their associated laboratory findings, and recommended diagnostic strategies are reviewed.

Hemophagocytic lymphohistiocytosis (HLH) is a rare disease with high mortality. Liver involvement is common (based on elevated liver function tests) with most patients demonstrating acute hepatitis. Liver biopsies are frequently obtained in the setting of suspected HLH for the purpose of identification of erythrophagocytosis, and if present, this finding is thought to suggest or support the diagnosis of HLH. However, there are problems with this approach; in particular, we do not know whether this finding is reproducible or whether it is specific to HLH. Therefore, we conducted a multi-institutional study in which experienced liver pathologists reviewed images taken from liver biopsies from patients with normal liver, acute hepatitis, possible HLH, and clinical HLH to determine if there was agreement about the presence or absence of erythrophagocytosis, and to ascertain whether the finding corresponds to a clinical diagnosis of HLH. Twelve liver pathologists reviewed 141 images in isolation (i.e., no clinical information or diagnosis provided). These came from 32 patients (five normal, 17 acute hepatitis, six HLH, four possible HLH). The pathologists classified each image as negative, equivocal, or positive for erythrophagocytosis. Kappa was .08 (no agreement) for case-level and 0.1 for image-level (1.4% agreement, based on two images which were universally considered negative). There was no difference in the proportion of pathologists who diagnosed erythrophagocytosis among those with different diagnoses at case or image-level (p = 0.82 and p = 0.82, respectively). Thus, erythrophagocytosis is an entirely unreliable histologic parameter in liver, as it is irreproducible and not demonstrably associated with a clinical disease (namely, HLH). Unless and until more reliable guidelines can be established, pathologists should refrain from commenting on the presence or absence of erythrophagocytosis in liver biopsy.

Hemophagocytic lymphohistiocytosis (HLH) is a rare but life-threatening condition. It is an immune-mediated disease that has a wide range of causes, elicits a hyperinflammatory response, and results in multiple organ damage. Clinical presentations vary, and in some cases, jaundice occurs as the first symptom.

We report the case of a 71-year-old female patient who presented with jaundice. She was admitted to our hospital because of the occurrence of "jaundice for half a month", and upon examination, obstructive jaundice with choledocholithiasis and gallstones was suggested. Cholecystectomy and choledocholithotomy were performed. However, the jaundice did not improve after surgery. We found splenomegaly, cytopenia, hypertriglyceridemia, hypofibrinogenemia, and elevated ferritin. Bone marrow biopsy revealed hemophagocytosis. Later, cardiac arrest occurred when she returned 3 wk after the surgery. We considered that HLH was triggered by septic shock. The patient's condition deteriorated rapidly, with multiple organ dysfunction and severe gastrointestinal bleeding. Corticosteroid therapy and symptomatic treatment failed to save her life.

Jaundice rarely presents as the first symptom in HLH patients. The HLH in this case was triggered by septic shock with jaundice as the first symptom. Clinicians should try hard to reduce missed diagnoses and misdiagnoses.

Hemophagocytic lymphohistiocytosis (HLH) is a rare multisystemic hyperinflammatory disease commonly associated with hepatic dysfunction. Liver injury is mediated by unchecked antigen presentation, hypercytokinemia, dysregulated cytotoxicity by natural killer and CD8 T cells, and disruption of intrinsic hepatic metabolic pathways. Over the past decade, there have been significant advances in diagnostics and expansion in therapeutic armamentarium for this disorder allowing for improved morbidity and mortality. This review discusses the clinical manifestations and pathogenesis of HLH hepatitis in both familial and secondary forms. It will review growing evidence that the intrinsic hepatic response to hypercytokinemia in HLH perpetuates disease progression and the novel therapeutic approaches for patients with HLH-hepatitis/liver failure.

Hemophagocytic Lymphohistiocytosis (HLH) is a group of disorders culminating in systemic inflammation and multi-organ failure with high incidence of hepatic dysfunction. Overproduction of IFN-γ is the main immunopathological driver in this disorder. Monokine induced by IFN-γ (CXCL9) serves as a biomarker for disease activity and response to treatment in this disorder. However, very little is understood about the actual functional role of CXCL9 in pathogenesis in HLH. In the current study, we sought to determine the role of CXCL9 in pathogenesis in murine models of both Familial HLH (prf1^-/-) and Toll Like Receptor (TLR) 9 repeated stimulation induced Macrophage Activation Syndrome (MAS), a form of secondary HLH. FHL and MAS were induced in both CXCL9 genetically deficient mice (cxcl9^-/-) and controls as well as using AMG487, a pharmacological antagonist of the CXCL9 receptor, CXCR3. Results showed that CXCL9 genetic deficiency did not improve disease parameters or hepatitis in both models. Consistent with genetic ablation of CXCL9, inhibition of its receptor, CXCR3, by AMG487 did not show any significant effects in the FHL model. Taken together, inhibition of CXCL9-CXCR3 interaction does not ameliorate HLH physiology in general, or hepatitis as a classical target organ of disease.

Acute liver failure following COVID-19 infection and/or vaccination is very rare and can be secondary to hemophagocytic lymphohistiocytosis (HLH). Liver injury in such cases appears to be extrinsic and thus treatment hinges on prompt diagnosis and reversal of the primary disease. We describe a patient who developed acute liver failure secondary to HLH after receiving a second dose of the Pfizer COVID-19 vaccine. Persistently elevated liver function tests, fevers, and cytopenia following COVID-19 vaccination should prompt clinicians to calculate an H-score to evaluate for the presence of HLH.

Pediatric acute liver failure (PALF) is a life-threatening disorder characterized by acute hepatocellular injury occurring in children without recognized underlying liver disease. The clinicopathologic evaluation of PALF requires a different approach from that in adults. The diagnostic considerations differ depending on the age, personal and family history, geographical region, and clinical presentation. Distinct entities such as gestational alloimmune liver disease, herpes simplex virus infection, and metabolic disorders should be considered in neonates with acute liver failure, while acetaminophen toxicity and autoimmune hepatitis are more frequently seen in older children and adolescents. An identified cause for PALF despite a negative complete evaluation (indeterminate) is lacking in 30 to 50% of cases. Although not routinely performed in the setting of PALF, liver biopsy may be helpful in assessing the etiology, potential mechanisms of injury, determining the appropriateness of liver transplantation, and prognostication of the patients. In this article, we review the clinicopathologic characteristics of PALF with an emphasis on general approach of pathologic evaluation and histopathologic characteristic of selected entities.

Interferon gamma (IFN-γ) is the main cytokine driving organ dysfunction in Familial Hemophagocytic Lymphohistiocytosis (FHL). Blockade of IFN-γ pathway ameliorates FHL hepatitis, both in animal models and in humans with FHL. Hepatocytes are known to express IFN-γ receptor (IFN-γ-R). However, whether IFN-γ induced hepatitis in FHL is a lymphocyte or liver intrinsic response to the cytokine has yet to be elucidated. Using a IFNgR-/- bone marrow chimeric model, this study showed that non-hematopoietic IFN-γ response is critical for development of FHL hepatitis in LCMV-infected Prf1-/- mice. Lack of hepatic IFN-γ responsiveness results in reduced hepatitis as measured by hepatomegaly, alanine aminotransferase (ALT) levels and abrogated histologic endothelial inflammation. In addition, IFN-γ non-hematopoietic response was critical in activation of lymphocytes by soluble interleukin 2 receptor (sIL-2r) and recruitment of CD8+ effector T lymphocytes (CD8+ CD44hi CD62Llo) (Teff) and inflammatory monocytes. Lastly, non-hematopoietic IFN-γ response results in increased hepatic transcription of type 1 immune response and oxidative stress response pathways, while decreasing transcription of genes involved in extracellular matrix (ECM) production. In summary, these findings demonstrate that there is a hepatic transcriptional response to IFN-γ, likely critical in the pathogenesis of FHL hepatitis and hepatic specific responses could be a therapeutic target in this disorder.

Hemophagocytic lymphohistiocytosis (HLH) is a complex, often under-recognized hyperinflammatory immune dysregulation syndrome arising in a diverse range of clinical scenarios and conditions. The accurate and timely diagnosis of HLH is crucial for patient survival, and usually requires a high level of clinical suspicion. The histologic corollary to clinical HLH - hemophagocytosis - is neither necessary nor sufficient for the diagnosis of HLH, as it may be seen in a variety of reactive conditions and may be absent in true HLH. Nevertheless, the finding of hemophagocytosis in specific clinical situations should prompt consideration of HLH and further testing to exclude the condition. While traditionally described in bone marrow, identification of hemophagocytosis in other tissues, including lymphoid, splenic, liver, or neural tissue, can be an important asset to the overall recognition of HLH. In this review we discuss the underlying pathophysiology and etiologies of HLH, morphologic aspects of hemophagocytosis and its associated histologic findings in different tissues, and give a brief overview of diagnostic criteria and clinical evaluation.

Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening disorder of immune regulation that can eventually result in end-organ damage and death. HLH is characterized by uncontrolled activation of cytotoxic T lymphocytes, natural killer cells, and macrophages that can lead to a cytokine storm. The diagnosis of HLH is often challenging due to the diverse clinical manifestations and the presence of several diagnostic mimics. The prognosis is generally poor, warranting rapid diagnosis and aggressive management.

To provide a comprehensive review of the pathogenesis, clinical features, diagnosis, and management of HLH.

Peer-reviewed literature.

HLH is a condition where a complete understanding of the pathogenesis, early diagnosis, and proper management has an important role in determining patient outcome. Genetic mutations causing impairment in the function of cytotoxic T lymphocytes and natural killer cells have been identified as the root cause of familial HLH; however, the specific pathogenesis of acquired HLH is unclear. The HLH-2004 protocol used in the diagnosis of HLH was originally developed for the pediatric population. The HLH-2004 protocol still forms the basis of the diagnosis of HLH in adults, although its use in adults has not been formally validated yet. Treatment of HLH is primarily based on the HLH-94 protocol, which involves suppressing the inflammatory response, but the treatment needs to be modified in adults depending on the underlying cause and comorbidities.

Acute liver failure is a life-threatening condition commonly caused by drug-induced hepatotoxicity or viral hepatitides. However, there are a number of rarer causes such as haemophagocytic lymphohistiocytosis. Haemophagocytic lymphohistiocytosis is a syndrome of uncontrolled immune cell activation, triggered by infection or malignancy, which carries a high mortality. Whilst mild to moderate liver injury is commonly seen with haemophagocytic lymphohistiocytosis, acute liver failure has rarely been reported in adults. We present a case of a 74-year-old man with acute liver failure secondary to haemophagocytic lymphohistiocytosis triggered by undiagnosed large B-cell lymphoma. Initially treated for biliary sepsis, there was a delay in the diagnosis of haemophagocytic lymphohistiocytosis and despite initiating chemotherapy, he died soon after. This case highlights the importance of considering haemophagocytic lymphohistiocytosis as a rare cause of acute liver failure, as given the life-threatening potential of haemophagocytic lymphohistiocytosis, a prompt diagnosis may allow early initiation of chemotherapy for any chance of survival.

A significant amount of clinical and research interest in thrombosis is focused on large vessels (eg, stroke, myocardial infarction, deep venous thrombosis, etc.); however, thrombosis is often present in the microcirculation in a variety of significant human diseases, such as disseminated intravascular coagulation, thrombotic microangiopathy, sickle cell disease, and others. Further, microvascular thrombosis has recently been demonstrated in patients with COVID-19, and has been proposed to mediate the pathogenesis of organ injury in this disease. In many of these conditions, microvascular thrombosis is accompanied by inflammation, an association referred to as thromboinflammation. In this review, we discuss endogenous regulatory mechanisms that prevent thrombosis in the microcirculation, experimental approaches to induce microvascular thrombi, and clinical conditions associated with microvascular thrombosis. A greater understanding of the links between inflammation and thrombosis in the microcirculation is anticipated to provide optimal therapeutic targets for patients with diseases accompanied by microvascular thrombosis.

Hemophagocytic lymphohistiocytosis (HLH) is a rare, life threatening hyperinflammatory syndrome. Sinusoidal hemophagocytosis is occasionally observed on liver biopsy in patients who do not have clinical suspicion of HLH. We aimed at comparing the clinical characteristics and outcomes of patients with signs of hemophagocytosis on liver biopsy meeting and not meeting the HLH diagnostic criteria.

We reviewed the clinical, laboratory features and outcomes of all adult patients consecutively admitted in our center between 08/2011 and 08/2017 presenting with liver histology showing sinusoidal hemophagocytosis and of critically ill patients presenting with severe liver disease in whom hemophagocytosis was histologically confirmed. The characteristics of patients fulfilling and not fulfilling the diagnostic criteria of HLH were compared.

We identified 12 cases (58% male, median age 61, 75% with a chronic underlying disease) with liver histology showing sinusoidal hemophagocytosis. All had at least some of the clinical features typically associated with HLH. Six were critical ill patients. In 4 cases with insufficient laboratory and clinical criteria, liver biopsy allowed to confirm the HLH diagnosis. Six patients died, of which four met the diagnostic criteria for HLH. Two patients with chronic liver disease died despite not fulfilling the diagnostic criteria of HLH.

Hemophagocytosis on liver biopsy may contribute to confirming a diagnosis of HLH in suspected cases with indeterminate clinical and laboratory findings. Sinusoidal hemophagocytosis in patients with cirrhosis was associated with bad outcome.

Describe a single center experience of hemophagocytic lymphohistiocytosis in a PICU over a 10-year period, to identify clinical features that may be associated with worse outcomes, including mortality, hospital and ICU length of stay, and functional and cognitive impairments on discharge.

Retrospective electronic medical record review, 2007-2017.

PICU located in a large urban academic quaternary care children's hospital.

All children admitted with hemophagocytic lymphohistiocytosis to our PICU from 2007 to 2017.

None.

All patients were identified utilizing International Classification of Diseases, 9th Revision and International Classification of Diseases, 10th Revision codes. Each chart was reviewed for demographic information, hemophagocytic lymphohistiocytosis diagnostic criteria, laboratory data, Pediatric Risk of Mortality Score III, clinical features and events of ICU stay, and PICU and hospital (length of stay). Mortality at 1 year and change in Functional Status Scale from admission to discharge were recorded. There were 42 admissions with 33 unique patients. Median Pediatric Risk of Mortality score at admission was 9 (interquartile range, 7-16). Median PICU length of stay was 7 days (interquartile range, 2-21 d) and hospital length of stay was 24 days (interquartile range, 14-37 d). During their ICU stay, 56% of patients received mechanical ventilation, 43% required vasoactives, 18% required continuous renal replacement therapy, and 5% received extracorporeal life support. Clinical factors related to increased PICU length of stay included Pediatric Risk of Mortality III score (p = 0.019), maximum lactate dehydrogenase (p = 0.017), maximum total bilirubin (p = 0.042), need for mechanical ventilation (p = 0.002), vasoactive use (p = 0.02), and secondary infection (p = 0.007). The most common therapies for hemophagocytic lymphohistiocytosis included steroids (93%), etoposide (55%), and anakinra (48%). Of the 26 patients who survived to hospital discharge, 19% had newly acquired morbidities. Overall 1-year mortality was 42%.

Hemophagocytic lymphohistiocytosis diagnosed in the PICU is a disease with high mortality. Patients who survive to discharge had relatively little morbidity, however, the mortality risk in the year following discharge continued to remain high.

The sensing of microbial genetic material by leukocytes often elicits beneficial pro-inflammatory cytokines, but dysregulated responses can cause severe pathogenesis. Genome-wide association studies have linked the gene encoding phospholipase D3 (PLD3) to Alzheimer's disease and have linked PLD4 to rheumatoid arthritis and systemic sclerosis. PLD3 and PLD4 are endolysosomal proteins whose functions are obscure. Here, PLD4-deficient mice were found to have an inflammatory disease, marked by elevated levels of interferon-γ (IFN-γ) and splenomegaly. These phenotypes were traced to altered responsiveness of PLD4-deficient dendritic cells to ligands of the single-stranded DNA sensor TLR9. Macrophages from PLD3-deficient mice also had exaggerated TLR9 responses. Although PLD4 and PLD3 were presumed to be phospholipases, we found that they are 5' exonucleases, probably identical to spleen phosphodiesterase, that break down TLR9 ligands. Mice deficient in both PLD3 and PLD4 developed lethal liver inflammation in early life, which indicates that both enzymes are needed to regulate inflammatory cytokine responses via the degradation of nucleic acids.

Autoinflammatory diseases are caused by pathologic activation of the innate immune system. Primary hemophagocytic lymphohistiocytosis (HLH) is an aggressive syndrome of excessive immune activation caused by monogenic mutations resulting in cytotoxic cell defects and subsequent failure to eliminate activated macrophages. Secondary HLH is often diagnosed in cases without a known Mendelian inheritance. However, some cases of "secondary" HLH have been shown to harbor mutations with partial dysfunction of the cytotoxic system. Recently, macrophage intrinsic abnormalities caused by NLRC4 inflammasome mutations have been linked to autoinflammation and recurrent macrophage activation syndromes resembling a primary HLH. We report a case of a former 28-week preterm infant with congenital anemia, ascites, and a heavy edematous placenta with fetal thrombotic vasculopathy, who developed hepatosplenomegaly and unexplained systemic inflammation with laboratory features of HLH in the early postnatal course and died at 2 months of age. Postmortem examination confirmed the hepatosplenomegaly with marked sinusoidal hemophagocytosis, along with striking hemophagocytosis in the bone marrow and lymph nodes. There was extensive acute and chronic ischemic bowel disease with matted bowel loops, fibrous adhesions, and patchy necrotizing enterocolitis features. Whole exome sequencing analysis demonstrated a novel mosaic heterozygous NLRC4 512 C> T (p.Ser171Phe) de novo mutation predicated to cause a dominant, gain-of-function mutation resulting in a constitutively active protein. The assembly of NLRC4-containing inflammasomes via an induced self-propagation mechanism likely enables a perpetuating process of systemic macrophage activation, presumed to be initiated in utero in this patient.

Chronic active Epstein-Barr virus infection (CAEBV) associated with hemophagocytic syndrome (HPS) and extra-nodal natural killer (NK)/T-cell lymphoma (ENKL) is a rare life-threatening disorder. This disease is easily misdiagnosed because of its varied presentations.

An 18-year-old girl was admitted to our hospital with a history of edema in the lower limbs and intermittent fever lasting for more than 1 month. At admission, she had severe liver injury of unknown etiology. Laboratory test results revealed pancytopenia, hyperferritinemia, hypertriglyceridemia, and hypofibrinogenemia. Results of serologic tests for EBV were positive. Results of a skin biopsy indicated EBV-positive NK/T-cell lymphoma, and bone marrow aspiration revealed focal hemophagocytosis and atypical lymphoid cells.

On the basis of these findings, we diagnosed the case as extra-nodal NK/T-cell lymphoma-associated HPS (natural killer/T-cell lymphoma-associated hemophagocytic syndrome), which is commonly induced by CAEBV.

Treatment consisted of general management of hepatitis, supplemented with albumin and empirical antibiotic therapy.

The patient died from massive gastrointestinal hemorrhage a week after she was discharged from the hospital.

ENKL and HPS present with varied features and are generally fatal; therefore, clinicians should proceed with caution in suspected cases. HPS should be considered when the patient presents with fever, hepatosplenomegaly, pancytopenia, and liver failure. When HPS is suspected, clinicians should determine the underlying cause, such as severe infection, including infection with viruses such as EBV; genetic predisposition; or underlying malignancies, especially lymphoma because of its strong association with HPS.

Hemophagocytic lymphohistiocytosis (HLH) is a rare disease that can be triggered by cytomegalovirus, a relatively common infectious exposure to neonates. The clinical presentation is common to many acute illnesses seen in extreme premature infants; however, there are key clinical and laboratory findings that can lead to the diagnosis.

We present a case of an extreme premature infant of 25 weeks' gestation who developed cytomegalovirus-induced HLH. Using the current published protocols that are used in pediatric cancer can be adapted for use in a premature infant, which led to remission of HLH and eventual discharge from the neonatal intensive care unit.

There are published treatment protocols used in pediatric oncology that when initiated early can lead to favorable outcomes and remission in even the most fragile neonates.

Additional studies are needed on the pharmacokinetics, dosing, and side effects on medications used for treatment of HLH in preterm infants. Additional research is needed to improve the clinician's ability to reach the diagnosis as well as define treatment strategies that provide optimal outcomes.

Hemophagocytic lymphohistiocytosis (HLH) is a rare condition that can be caused by a primary or acquired disorder of uncontrolled immune response. Liver injury is a common complication of HLH; however, HLH presenting as acute liver failure (ALF) has rarely been reported in adults.

A 34-year-old man was admitted to our hospital with nausea and fatigue persisting for 2 weeks and jaundice for 1 week. He had hyperthermia at the onset of disease. At admission, he had severe liver injury with unknown etiology. The laboratory data showed that he had hyperferritinemia, thrombocytopenia, anemia, hypertriglyceridemia, and hypofibrinogenemia. Finally, a bone marrow biopsy revealed hemophagocytic cells, and he was diagnosed with HLH. The patient was treated with prednisone and plasma exchange. However, the liver function of the patient deteriorated, and he finally died of multiorgan failure.

Reports of adult patients with ALF caused by HLH have increased, and HLH should be suspected in patients with ALF of indeterminate cause. Although the efficacy of the treatment strategy recommended by the HLH 2004 remains to be confirmed in adult patients with ALF caused by HLH, early diagnosis and prompt combined treatment with steroids and cyclosporin A or etoposide should be emphasized.

Ipilimumab is a monoclonal antibody that inhibits the CTLA4 receptor on cytotoxic T lymphocytes, resulting in immune-mediated tumor cell death. Ipilimumab is most often used in the treatment of metastatic melanoma, and rarely liver toxicity necessitating cessation of treatment occurs. The aim of this study was to characterize the histologic features and clinical course of ipilimumab-associated hepatitis. Eleven patients with clinical suspicion of ipilimumab-induced hepatitis, due to the development of abnormal liver function tests (LFTs) while receiving treatment, and who underwent liver biopsy, were identified over a 6-year period. Ten patients were male and 1 female (median age 58 y), and all received 1 to 4 doses of ipilimumab. None had known preexisting liver disease. Two patients were obese, and another had a history of alcohol abuse. Viral and autoimmune serologies were negative in all patients except 1 who had a mildly elevated ANA titer. Nine biopsies showed active hepatitis with 2 distinct histologic patterns: panlobular hepatitis in 6 cases and zone 3 hepatitis in 3. The inflammatory infiltrate was similar in composition in both patterns, composed predominantly of CD8+ T lymphocytes, admixed histiocytes, scattered plasma cells, and eosinophils. Prominent histiocytic sinusoidal infiltrates were present in 7 cases and frequently formed loose histiocytic aggregates. Central vein endothelialitis was present in 8 cases. Patients in this group tended to have markedly elevated ALT, AST, and total bilirubin. Two cases did not fit into the above 2 histologic groups: 1 showed portal inflammation with cholangitis, and the other showed morphologic features indistinguishable from nonalcoholic steatohepatitis. Discontinuation of ipilimumab and administration of immunosuppressives resulted in resolution or marked improvement of LFTs in all patients within 3 months of presentation. Ipilimumab may potentially unmask previously subclinical liver disease, for example, fatty liver disease, and the diagnosis of ipilimumab-induced liver injury may only be recognized with certainty after cessation of the drug leads to normalization of LFTs. Overall, ipilimumab-associated hepatitis most often presents with a panlobular active hepatitis that resembles autoimmune hepatitis. Prominent sinusoidal histiocytic infiltrates and central vein damage with endothelialitis may be helpful histologic clues to the diagnosis of ipilimumab-associated hepatitis.

Children with acute liver failure (ALF) caused by hemophagocytic lymphohistiocytosis (HLH) may be at risk of undergoing unnecessary liver transplantation (LT). The aim of this study was to compare the characteristics of ALF caused by HLH with those of ALF of unknown etiology in children.

The clinical features and laboratory findings for eight children with ALF caused by HLH (ALF-HLH group) and 27 children with ALF of unknown etiology (ALF-UK group) were retrospectively compared by reviewing medical records.

The ALF-HLH group had a higher incidence of pleural effusion, C-reactive protein elevation (especially >5 mg/dL), thrombocytopenia, anemia, fever, splenomegaly, and hypoalbuminemia (<2.5 mg/dL), and a higher in-hospital mortality rate. No significant differences were found in the white blood cell count, liver enzymes, coagulation profile, or incidence of hepatomegaly.

LT should be performed only after it is proven that ALF is not caused by HLH, if a child with ALF shows the differential clinical features of ALF caused by HLH. Further research with larger sample sizes, however, is needed.

Hemophagocytic lymphohistiocytosis (HLH) is a frequently fatal and likely underdiagnosed disease involving a final common pathway of hypercytokinemia, which can result in end-organ damage and death. Although an early diagnosis is crucial to decrease mortality, the definitive diagnosis is often challenging because of the lack of specificity of currently accepted diagnostic criteria and the absence of confirmatory gold standards. Because of the wide range of laboratory assays involved in the diagnosis of HLH, practicing pathologists from a broad spectrum of clinical specialties need to be aware of the disease so that they may appropriately flag results and convey them to their clinical counterparts. Our article summarizes these new advances in the diagnosis of HLH and includes a review of clinical findings, updated understanding of the pathogenesis, and promising new testing methods.

Haemophagocytic lymphohistiocytosis (HLH) is a hyperinflammatory disorder resulting from immune dysfunction reflecting either primary immune deficiency or acquired failure of normal immune homeostasis. Familial HLH includes autosomal recessive and X-linked disorders characterized by uncontrolled activation of T cells and macrophages and overproduction of inflammatory cytokines, secondary to defects in genes encoding proteins involved in granule-dependent cytolytic pathways. In older children and adults, HLH is associated more often with infections, malignancies, autoimmune diseases, and acquired immune deficiencies. HLH, macrophage activation syndrome, sepsis, and systemic inflammatory response syndrome are different clinical entities that probably represent a common immunopathological state, termed cytokine storm. These conditions may be clinically indistinguishable; all include massive inflammatory response, elevated serum cytokine levels, multi-organ involvement, haemophagocytic macrophages, and often death. Tissues of haematopoietic and lymphoid function are directly involved; other organs are secondarily damaged by circulating cytokines and chemokines. Haemophagocytic disorders are now increasingly diagnosed in the context of severe inflammatory reactions to viruses, malignancies and systemic connective tissue diseases. Many of these cases may reflect underlying genetic predispositions to HLH. The detection of gene defects has contributed considerably to our understanding of HLH, but the mechanisms leading to acquired HLH have yet to be fully determined.

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening condition due to the association of an infectious agent with lymphocyte cytotoxicity defects, either of congenital genetic origin in children or presumably acquired in adults. In HLH patients, an excess of lymphocyte or macrophage cytokines, such as IFN-γ and TNFα is present in serum. In animal models of the disease, IFN-γ and TNF-α have been shown to play a central pathogenic role. In humans, unusually high concentrations of IL-18, an inducer of IFN-γ, and TNF-α have been reported, and are associated with an imbalance between IL-18 and its natural inhibitor IL-18 binding protein (IL-18BP) resulting in an excess of free IL-18. Here we studied whether IL-18BP could reduce disease severity in an animal model of HLH. Mouse cytomegalovirus infection in perforin-1 knock-out mice induced a lethal condition similar to human HLH characterized by cytopenia with marked inflammatory lesions in the liver and spleen as well as the presence of hemophagocytosis in bone marrow. IL-18BP treatment decreased hemophagocytosis and reversed liver as well as spleen damage. IL-18BP treatment also reduced both IFN-γ and TNF-α production by CD8(+) T and NK cells, as well as Fas ligand expression on NK cell surface. These data suggest that IL-18BP is beneficial in an animal model of HLH and in combination with anti-infectious therapy may be a promising strategy to treat HLH patients.

Recent studies pertaining to the histopathology of the liver and biliary tract are reviewed.

Several studies are reviewed which describe the histologic features and clinical behavior of 'plasma cell hepatitis' in the posttransplant setting. Cytokeratin 7, EMA, and CD68 were found to be useful immunohistochemical stains in fibrolamellar hepatocellular carcinoma and may aid in the distinction between this variant and classic hepatocellular carcinoma. Arginase-1, another immunohistochemical stain, was found to have improved sensitivity over HepPar-1 in the diagnosis of classic hepatocellular carcinoma. Metabolic syndrome is common in children with nonalcoholic fatty liver disease and may be an indicator of more severe disease activity and fibrosis. Histologic features were described that may aid in the distinction between the steroid-responsive IgG4-associated cholangitis and the steroid-nonresponsive primary sclerosing cholangitis. In addition, immunohistochemical stains for IgM and IgG may be helpful in distinguishing between autoimmune liver diseases, with primary biliary cirrhosis and its antimitochondrial-negative variant, autoimmune cholangitis, being the two autoimmune liver diseases with a predominance of IgM-positive plasma cells.

Several informative studies pertaining to hepatobiliary pathology were published this year, with topics including posttransplant plasma cell hepatitis, familial hemophagocytic lymphohistiocytosis, pediatric nonalcoholic fatty liver disease, and the use of immunohistochemical stains specific for various immunoglobulin subtypes.