Supplementary Material for: Nephropathy in a Child with Severe Recessive Dystrophic Epidermolysis Bullosa Treated with Cyclophosphamide: A Case Report

Long-term inflammation and recurrent skin infections in recessive dystrophic epidermolysis bullosa (RDEB) are associated with the presence of immunoglobulin A (IgA)-containing immune complexes in the glomerulus. Only eight pediatric RDEB cases with IgA nephropathy (IgAN) have been documented in English-language literature. Most RDEB patients with IgAN progress to kidney failure within five years of diagnosis, indicating that these patients may require more intensive early treatment compared to those with primary IgAN. However, diagnosing IgAN in RDEB cases with severe cutaneous manifestations can be challenging. Herein, we report a rare case of nephropathy in an 11-year-old boy with severe RDEB and a frameshift mutation on the COL7A1 gene, which may manifest as kidney disorders. He presented with persistent hematuria and progressing proteinuria. A presumptive IgAN diagnosis was based on clinical features and increased IgA serum levels, as kidney biopsy was refused by his parents. Nephrotic-range proteinuria persisted despite initial steroid and lisinopril treatment. Monthly intravenous cyclophosphamide (IV CPA; 500 mg/m2) led to proteinuria remission and preservation of kidney function for two years post-treatment. We conclude that COL7A1 mutations may result in extracutaneous manifestations, including kidney disorders. The association between IgA-containing immune complex deposits in the glomerulus and recurrent skin infections in RDEB may indicate IgAN, particularly when kidney biopsy is infeasible due to severe skin manifestations. In our case, positive results with IV CPA suggest further investigation is needed to explore its potential role in non-rapidly progressing IgAN in children with RDEB.