A 22-year-old white male presents with a history of microscopic hematuria and albuminuria. He also complains of a steady deterioration in his hearing, accompanied intermittently by low-pitched tinnitus in both ears in the past 5 years. Family history is notable for an uncle who developed kidney failure. Pure-tone audiometry with speech testing confirmed bilateral moderate sensorineural hearing loss. Complete blood count showed normal values. Blood urea nitrogen (BUN) and creatinine levels were elevated at 42 and 2.6 mg/dL, respectively. Chest X-ray and ECG were normal. Ultrasound of the kidneys was normal. A percutaneous kidney biopsy showed the following electron micrograph (see pic). What is the diagnosis?