Background. Amyloidosis is a group of disorders with extracellular accumulation of autologous fibrillary insoluble proteins in various tissues and organs such as the kidneys, liver, spleen, heart and gastrointestinal tract leading to impairment of normal organ function. Childhood amyloidosis is an exceedingly rare entity mainly caused by familial Mediterranean fever (FMF) and the other autoinflammatory diseases such as mevalonate kinase deficiency (MKD).

Case. A 16-year-old male was referred to pediatric nephrology for coincidentally discovered proteinuria. He had no significant findings on physical examination except for urochromic color. He had nephrotic range proteinuria with 109 mg/m2/h and serum creatinine was 1.35 mg/dl. Kidney biopsy was performed because of nephrotic range proteinuria with acute kidney injury. In hematoxylin-eosin-stained tissue sections, amyloid was suggested as extracellular amorphous material that is lightly eosinophilic in the glomeruli. Diagnosis was confirmed by Congo red positivity, with apple-green birefringence under polarized light. MEFV gene mutation was negative and a compound heterozygote mutation found in mevalonate kinase gene. A 6-monthtrial of colchicine, enalapril, and losartan combination was not successful; Canakinumab was started thereafter. Proteinuria and creatinine decreased to 7 mg/m2/h and 0.6 mg/dl respectively 4 years after treatment.

Conclusions. Amyloidosis should be considered especially in children presenting with proteinuria and with a history of recurrent fever. This report also emphasizes the efficacy of canakinumab to prevent or decelerate chronic renal failure in these patients although it does not reduce tissue deposition in long-term use.

Keywords: amyloidosis, canakinumab, kidney injury, mevolonate kinase deficiency