Amyloidosis is a heterogeneous group of disorders characterized by extracellular deposition of unique protein fibrils. The least common presentation of an amyloid deposition is as a discrete mass called amyloidoma or amyloid tumor. We report a case of a soft tissue amyloidoma in the abdomen of a 16-year-old girl who was diagnosed as having systemic amyloidosis. A girl aged 16 years was referred to our hospital with a pre-diagnosis of a retroperitoneal mass documented with abdominal ultrasonography and tomography. A laboratory examination revealed nephrotic syndrome. She underwent surgery for a complete resection of the lesion. A histopathologic examination with Congo red and crystal violet dyes verified the diagnosis of amyloidoma. An immunohistochemical study for amyloid A protein was positive. A renal biopsy was also compatible with AA amyloidosis. A detailed search for the etiology of systemic amyloidosis revealed heterozygous mutation in the Mediterranean fever gene. Treatment with colchicine and anakinra were started with the diagnosis of familial Mediterranean fever because the other causes of secondary amyloidosis were ruled out. After 3 months of anakinra treatment, the laboratory findings returned to normal and excessive proteinuria disappeared. In countries where FMF and other autoinflammatory diseases are prevelant, systemic amyloidosis should be kept in mind in the differential diagnosis of children who present with nephrotic syndrome and abdominal mass. Taking previously reported cases and our case together, it appears that anti-interleukin-1 treatment represents a promising new approach in a subset of patients with systemic amyloidosis secondary to autoinflammatory diseases.
Keywords: amyloidoma; anakinra; familial Mediterranean fever; pediatric; systemic AA amyloidosis.
© 2017 Asia Pacific League of Associations for Rheumatology and John Wiley & Sons Australia, Ltd.