Systemic-onset juvenile idiopathic arthritis complicated by early onset amyloidosis in a patient carrying a mutation in the MEFV gene.

Systemic juvenile idiopathic arthritis (SJIA) is a disorder characterized by arthritis in children starting before 16 years of age associated with daily high fever, persisting for more than 2 weeks, and at least one of the following clinical features: evanescent cutaneous rash, lymphadenopathy, serositis or hepatosplenomegaly. SJIA patients carry a significantly higher frequency of MEFV mutations, the gene responsible for familial Mediterranean fever, and may be characterized by a more aggressive disease. In this line, we describe a 9-year-old girl affected with SJIA who carried a heterozygous G196W mutation in MEFV. Our patient was characterized by an aggressive disease course, resistance to conventional immunosuppressive agents and developed renal amyloidosis just 2 years after the disease onset.