Acute nephritic syndrome as the sentinel presentation of class III A lupus nephritis in a young patient

Abstract

Lupus nephritis (LN) is one of the most serious manifestations of Systemic lupus erythematosus (SLE), occurring in 50-75% of children with SLE, with over 90% developing renal involvement within two years of diagnosis. We describe a diagnostically challenging case of a 12-year-old girl presenting with nephritic syndrome, in whom further evaluation revealed an underlying diagnosis of Systemic lupus erythematosus (SLE). Investigations revealed hypocomplementemia (C3 21.0 mg/dl, C4 1.6 mg/dl), positive antinuclear antibody (ANA IF titre 1:80, ANA ELISA 7.9), strongly positive anti-double-stranded DNA (anti-dsDNA +++), significant proteinuria on 24-hour collection (888 mg/day), and microscopic haematuria. She fulfilled three of eleven American college of rheumatology (ACR) 1997 criteria for SLE. Light microscopy demonstrated focal segmental endocapillary hypercellularity with focal mesangial prominence. Renal biopsy confirmed focal proliferative lupus nephritis (ISN/RPS Class IIIA) with a NIH activity index of 3/24 and a characteristic ‘full house’ immunofluorescence pattern comprising deposits of IgG (2+), IgA (3+), IgM (1+/2+), C3 (1+/2+), C1q (3+), kappa (1+/2+), and lambda (2+). This case underscores the importance of maintaining a high index of suspicion for SLE in children with nephritic features and hypocomplementemia. Renal biopsy is essential for definitive classification and treatment planning even when ACR criteria are not fully met. Early histopathological diagnosis and class-guided immunosuppressive therapy are critical to preventing progression to end-stage renal disease in paediatric lupus nephritis.