Pediatric double-seropositive anti-glomerular basement membrane antibody disease: A case report and literature review.

Introduction: Glomerular basement membrane (GBM) disease is a severe and exceedingly rare disorder characterized by the presence of circulating antibodies targeting the non-collagen NC1 domain of the α3 chain of collagen type IV in glomerular and alveolar basement membranes. It typically presents as rapidly progressive glomerulonephritis (RPGN), often accompanied by pulmonary hemorrhage. The occurrence of double-seropositivity for anti-GBM antibody and anti-neutrophil cytoplasmic antibody (ANCA), primarily with myeloperoxidase specificity (MPO-ANCA), is particularly uncommon in pediatric cases.

Case presentation: A 9-year-old boy was admitted to the pediatric ward exhibiting macroscopic hematuria, proteinuria, and acute kidney injury, with a gradual decline in kidney function. Pulmonary function remained normal. Circulating anti-GBM antibodies and ANCA, specifically targeting myeloperoxidase (MPO), were detected. Diagnosis was confirmed via percutaneous renal biopsy, which revealed circular glomerular crescents in 9 out of 16 glomeruli. Immunofluorescence examination exhibited a linear staining pattern of the capillary wall for IgG. Treatment involved 5 boluses of methylprednisolone, followed by prolonged oral prednisone, 11 plasma exchange sessions, and initiation of rituximab due to a moderate response to therapy. Subsequently, the patient's condition significantly improved, with normalized renal function observed 24 months post treatment.

Conclusion: Despite limited literature on pediatric anti-GBM and double-positive disease, it is imperative to consider these diagnoses in pediatric patients presenting with RPGN. This article offers a comprehensive summary of the main characteristics of this disease in children and emphasizes therapeutic approaches through a review of identified cases in individuals under 18 years of age.