From Pseudo-Surgical Abdomen to Renal Amyloidosis: Delayed Diagnosis of Familial Mediterranean Fever in an Adolescent.

Familial Mediterranean fever (FMF) is an autosomal recessive autoinflammatory disease characterized by recurrent febrile episodes and serositis. Delayed diagnosis remains a major concern, as it may lead to severe complications, particularly AA amyloidosis. We report the case of a male patient, born to a consanguineous family, with recurrent episodes of fever and abdominal pain since early childhood, initially leading to an unnecessary appendectomy. The diagnosis of FMF was established at the age of 13 following the onset of nephrotic syndrome. Renal biopsy confirmed AA amyloidosis, and genetic testing revealed a homozygous M694V mutation in the MEFV gene. Despite colchicine therapy, persistent disease activity required initiation of anakinra, later switched to canakinumab due to ongoing subclinical inflammation, evidenced by an elevated serum amyloid A level with normal C-reactive protein. This case highlights the consequences of delayed diagnosis in FMF, the importance of early recognition in patients with recurrent abdominal pain, and the role of serum amyloid A in disease monitoring. It also illustrates intrafamilial phenotypic variability and the need for therapeutic escalation in colchicine-resistant disease.