Dense deposit disease in an adolescent male mimicking acute post-streptococcal glomerulonephritis.

Background: Dense deposit disease (DDD), a subtype of complement factor 3 glomerulopathy (C3G), is a rare entity associated with dysregulation of the alternative complement pathway. It usually affects children, with a 50% likelihood of progression to end-stage renal disease within ten years of diagnosis. Description of the case: We report the case of an adolescent male with acute nephritic syndrome and nephrotic range proteinuria, initially diagnosed as acute post-streptococcal glomerulonephritis (APSGN). Despite his spontaneous improvement, renal biopsy, performed due to a persistently low C3 level for over 18 weeks, confirmed the diagnosis of DDD. Complement and genetic studies showed high levels of C3-nephritic factor and risk polymorphisms for developing the disease. He was treated with prednisolone and mycophenolate mofetil (MMF). At the last follow-up, 15 months from onset, the serum creatinine level and 24h-hour total protein excretion were normal.

Conclusions: C3G (including the DDD subtype) should be suspected in apparent APSGN with atypical clinical features at presentation/follow-up, even in the case of spontaneous improvement. Timely and accurate diagnosis, based on histopathological, complement, and genetic studies, is important to initiate the appropriate treatment aimed at preventing or slowing the disease progression. HIPPOKRATIA 2020, 24(4): 191-193.