C1q Nephropathy in an Adolescent: A Clinical Diagnostic and Management Challenge

Abstract

C1q nephropathy is a rare glomerulopathy characterized histologically by dominant deposits of C1q protein in the glomerular mesangium, observed by immunofluorescence. Clinically, it usually manifests as nephrotic syndrome, severe proteinuria, hematuria, and arterial hypertension with corticodependent behavior. Its diagnosis represents a challenge, due to the similarity in clinical presentation with other glomerulopathies and the absence of established diagnostic criteria. We present the case of a 17-year-old adolescent with a history of nephrotic syndrome at the age of 2 years, with corticosensitive behavior in remission for a decade. From the age of 14 she presented frequent relapses, corticosteroid dependence and persistent proteinuria, despite the use of second-line immunosuppressants and negative rheumatologic tests. Due to his atypical evolution, a renal biopsy was performed and revealed glomeruli with minimal mesangial proliferation and predominant C1q deposits, confirming the diagnosis. This clinical case highlights the importance of considering C1q nephropathy in patients with corticodependent glomerulopathies and persistent proteinuria. Early and timely diagnosis is crucial to prevent progression to chronic renal failure. Treatment remains a challenge, given the high relapse rate and the need for prolonged immunosuppression. In the absence of specific clinical guidelines for the pediatric population, this report emphasizes the need to continue investigating its pathophysiology and possible predisposing genetic factors, in order to improve prognosis and develop more specific therapies.