Successful control of recurrent MAS by canakinumab in a Sjögren syndrome patient with homozygous MEFV P369S variants and review of literatures.

Macrophage activation syndrome (MAS) is an autoinflammatory condition, which severely complicates autoimmune diseases, such as systemic juvenile idiopathic arthritis, adult onset Still's disease, and systemic lupus erythematosus. MEFV gene encodes a component of pyrin inflammasome, whose variants cause familial Mediterranean fever (FMF). We experienced a recurrent MAS case with homozygous MEFV P369S variants accompanied by Sjögren syndrome and pulmonary arterial hypertension, whose recurrent MAS was successfully treated with canakinumab. Pathogenicity of MEFV P369S variant is still inconsistent, and clinical interpretation of this variant is challenging. Thus, we reviewed previous literatures and revealed that the majority of FMF patients with collagen diseases in carried MEFV P369S variant, all of which were reported from Japan. In this case-based review, we clarify the epidemiology of MEFV variants in collagen diseases and discuss the significance of their genetic analysis.