Systemic Juvenile Idiopathic Arthritis with Amyloidosis: An Uncommon Complication with a Favourable Outcome

Excerpt

To the Editor : Secondary amyloidosis is an uncommon complication of systemic onset juvenile idiopathic arthritis (sJIA) and till recently, was thought to be virtually irreversible with a poor outcome [1]. We report a 10-y-old boy, who was diagnosed to have sJIA based on typical quotidian fever, rash, serositis and hepatosplenomegaly. Rheumatoid factor and anti-nuclear antibodies were not detectable. Two and a half years later, he was found to have nephrotic range proteinuria. Renal biopsy showed deposition of amorphous, extracellular, pale eosinophilic and PAS negative material in the mesangium (Fig. 1a). The material was congophilic (Fig. 1b) with apple-green birefringence under polarizing microscopy (Fig. 1c). Immunohistochemistry for serum amyloid A (SAA) was positive in the glomerular basement membrane, mesangium and the vascular wall (Fig. 1d). He showed significant response in fever and arthritis with subcutaneus methotrexate, but proteinuria persisted. Hence, he was started on tocilizumab at a dose of 8 mg/kg every 4 wk. Proteinuria subsided within 6 mo. He has been on tocilizumab for past 2 y with normal renal functions and proteinuria free duration of 18 mo.

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