A 7-year-old boy presents following the passage of red-colored urine one day ago. This was limited to a single episode and resolved spontaneously. He had experienced a mild fever and sore throat for the preceding four days, but these symptoms have resolved now. There is no history of dysuria or urinary frequency. His medical history is unremarkable, and he is not on any drugs currently. His growth and development are age appropriate, and all immunizations are up to date. His family history is significant for chronic kidney disease in a maternal uncle at the age of 25 years. However, the underlying cause is unknown, and medical documentation in this respect is unavailable. Urinalysis reveals microhematuria, microalbuminuria, erythrocyte casts, and dysmorphic cells. A complete blood count, liver profile, renal profile, and serum electrolyte assay are all within normal parameters.
Both kidneys are of normal size, and both show increased cortical echogenicity. The urinary tract appears normal with no evidence of obstruction, cysts, or anatomic abnormalities.
Audiometry shows bilateral severe sensorineural hearing loss for the frequencies in the 2000 to 8000 Hz range.
Electron microscopy of the biopsy specimens shows thickening, lamelization, and fragmentation of the glomerular basement membrane (GBM). Immunohistochemistry shows a complete absence of immunostaining for all constitutive collagen IV chains (α3, α4, and α5) in both the GBM and Bowman's capsule.
Molecular genetic testing reveals a mutation of the COL4A5 gene.