Fanconi syndrome is a generalized proximal tubular dysfunction. Which combination of urinary findings is pathognomonic?

• A Proteinuria, hematuria, glucosuria, and high anion gap metabolic acidosis
• B Glucosuria in isolation with normal serum glucose — 'renal glycosuria'
• C Glycosuria, aminoaciduria, phosphaturia, uricosuria with normal blood glucose and non-anion gap metabolic acidosis (proximal RTA) ✓
• D Aminoaciduria with hyperammonemia — a urea cycle defect

Explanation

Fanconi syndrome results from dysfunction of the proximal tubule, which normally reabsorbs glucose, amino acids, phosphate, uric acid, K+, Na+, HCO3−, and low-MW proteins. The hallmark is glycosuria at normal blood glucose (failure of SGLT2), aminoaciduria, phosphaturia, uricosuria, hypophosphatemia, and proximal renal tubular acidosis (Type 2 RTA — failure to reabsorb HCO3− causing non-anion gap acidosis). Causes include Wilson's disease, cystinosis, multiple myeloma, heavy metal toxicity, and tenofovir toxicity.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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