A 15 year old male presents with hematuria. He has previous diagnoses of deafness and corneal dystrophy. Urinalysis shows 1 + proteins, no ketones, no glucose, 1+blood, and no leukocytes. A renal biopsy reveals tubular epithelial foam cells by light microscopy. By electron microscopy, the glomerular basement membrane shows areas of attenuation, with splitting and lamination of lamina dense in other thickened areas. The most probable diagnosis is -