Challenges and insights raised by comorbidity with FMF and selective IgA deficiency

Background

: Familial Mediterranean Fever (FMF) is the most common form of genetic autoinflammatory disease worldwide. In turn, selective IgA deficiency (SIgAD) is the most common humoral primary immunodeficiency, yet most patients remain asymptomatic. Case Presentation: A Jewish Brazilian female came to our attention due to recurrent inflammatory febrile episodes since very early in life, initially attributed to unexplained infections linked to SIgAD. At the age of 15 years, disabling buttock pain prompted a sacroiliac MRI, which demonstrated sacroiliitis. Direct genetic sequencing of the MEFV gene confirmed the diagnosis of FMF. After severe gastrointestinal intolerance to colchicine was observed, canakinumab achieved clinical and radiological control, enabling the reinstatement of colchicine. Conclusion: Here we report the first case of concomitant FMF and SIgAD in a Brazilian patient, highlighting the relevance of these comorbidities in the patient's diagnosis and follow-up. This coincidental association also provides insight into interactions between serum and mucosal IgA and the pyrin inflammasome in the control of inflammation and gut dysbiosis.