Re-evaluating the MYH9 p.I1816V variant in a patient with atypical clinical presentation

MYH9-related disease (MYH9-RD) is an autosomal dominant disorder typically characterized by macrothrombocytopenia, leukocyte inclusion bodies, and variable non-hematologic manifestations such as hearing loss and nephropathy. We herein describe a 16-year-old boy presenting with persistent proteinuria and biopsy-proven membranous nephropathy with focal segmental sclerosis. Genetic testing identified a rare MYH9 variant (p.I1816V), previously reported in association with Epstein syndrome. However, the patient had normal platelet counts, no leukocyte inclusions, and no abnormalities in non-muscle myosin heavy chain IIA (NMMHC-IIA) expression in neutrophils or podocytes. Although globally rare, the p.I1816V variant is more frequent in East Asian populations and is predicted to be benign by multiple in silico tools. This case illustrates the challenges of interpreting rare variants in the absence of supportive clinical findings and highlights the need for cautious evaluation in the era of next-generation sequencing.