Published online Jan 26, 2026. doi: 10.12998/wjcc.v14.i3.117165
Revised: December 15, 2025
Accepted: January 6, 2026
Published online: January 26, 2026
Processing time: 53 Days and 9.9 Hours
Familial Mediterranean fever (FMF) is the most common autoinflammatory disease, characterized by uncontrolled activation of the innate immune system that manifests as recurrent fever and polyserositis (e.g., peritonitis, pleuritis, and arthritis). However, diagnosing atypical cases remains challenging.
A 9-year-old girl had a history of progressive loss of appetite, weight loss, and myalgia over the preceding three months. She developed high-grade fever over the preceding three weeks, occasionally associated with abdominal pain. The girl is one of a triplet; neither of the other two sisters had similar symptoms. Family history was irrelevant. She presented with cachexia, generalized body aches, and fever without evident arthritis. She had splenomegaly and a markedly elevated erythrocyte sedimentation rate. After exclusion of rheumatological and malignant causes, FMF was suspected. Serum amyloid A was high. The patient received colchicine therapy. There was a significant improvement in her symptoms with normalization of acute-phase reactants. Polymerase chain reaction test for FMF gene mutation returned negative.
FMF can present with atypical symptoms. Detailed history and meticulous clinical evaluation were key clues suggesting the diagnosis.
Core Tip: Familial Mediterranean fever is classically defined by recurrent episodes of spontaneous serositis with fever, but some children present with significant inflammation despite lacking these typical features. This case describes a 9-year-old girl with cachexia, debilitating myalgia, and recurrent fever, an atypical phenotype that created substantial diagnostic difficulty, especially with negative MEditerranean FeVer gene mutation testing. Her course underscores how familial Mediterranean fever may manifest beyond standard criteria and why clinicians must look beyond genetic results. A detailed history and careful clinical assessment were ultimately key to recognizing the disease.