Olfactory dysfunction in antineutrophil cytoplasmic antibody-associated vasculitides: A review of the literature

Table 1 Causes and mechanisms involved in the development of antineutrophil cytoplasmic antibody-associated vasculitides olfactory dysfunction

Ref.	Population	Findings
Conductive causes
Laudien et al[11], 2009	76 GPA patients	No correlation between localised disease and a higher degree of olfactory dysfunction
Laudien et al[15], 2010	89 GPA patients	No correlation between olfactory function and colonisation with Staphylococcus aureus
Fasunla et al[6], 2012	16 GPA patients	No difference in the olfactory performance between patients with and without septal perforation
Proft et al[8], 2014	44 GPA patients	Decrease in olfactory function could be a consequence of the inflammatory disease in the nose rather than the local manifestations (bloody nasal discharge, crusting, granulomata)
Zycinska et al[9], 2016	43 GPA patients	Active and chronic sinonasal inflammation (rhinosinusitis) in GPA patients seems to be the more likely cause for the reported olfactory dysfunction. Olfactory dysfunction is more common in GPA patients with increased crusting, pathological granulation but also a higher Lund-MacKay score
Sensorineural causes
Fauci et al[17], 1983	85 GPA patients	Cranial nerve involvement reported in 7.4% of GPA patients
Nishino et al[18], 1993	324 GPA patients	Cranial nerves involvement reported in 6.5% of GPA patients even if first cranial nerve was rarely involved
Other factors
Laudien et al[11], 2009	76 GPA patients	GPA patients receiving local mupirocin treatment showed no olfactory dysfunction. No correlation between kidney involvement and smell function
Göktas et al[7], 2010	9 GPA patients	Neither the disease duration nor the age appear to influence smell function
Fasunla et al[6], 2012	16 GPA patients	No correlation between kidney involvement and smell function. GPA patients with and without past history of sinonasal operations did not show any significant difference in sense of smell
Proft et al[8], 2014	44 GPA patients	GPA patients with elevated CRP values showed lower scores from smell tests. GPA patients with a higher extent of damage showed a tendency for reduced scores only for the threshold, but not for the identification, the discrimination or the total score (TDI score). No correlation between kidney involvement and smell function. GPA patients under therapy with azathioprine showed significantly lower scores only for odour discrimination. GPA patients undergoing low-dose GC therapy showed a tendency for lower thresholds scores compared to patients without GC therapy
Tallab et al[12], 2014	1 EGPA patient	Subjective improvement of smell function after immunosuppressive therapy

GPA: Granulomatosis with polyangiitis; EGPA: Eosinophilic granulomatosis with polyangiitis; CRP: C-reactive protein; GC: Glucocorticoids.