Fanconi syndrome is a condition characterized by impaired reabsorption of multiple substances in the proximal renal tubules, leading to excessive urinary loss of amino acids, glucose, phosphates, bicarbonate, and other substances. This results in proximal renal tubular acidosis, hypokalemia, rickets, osteoporosis, and growth retardation. The syndrome can be caused by various hereditary or acquired diseases. There are two possible common mechanisms underlying this condition: first, altered integrity of the renal tubular membrane leading to a "leakage" phenomenon that prevents effective reabsorption of multiple solutes; second, metabolic changes within the tubular cells that impair their ability to generate sufficient energy for substance transport. These two mechanisms are sometimes inseparable, as maintaining cellular integrity and tubular epithelium requires intracellular energy.

bubble_chart Clinical Manifestations

Commonly seen are growth retardation and rickets. Chronic metabolic acidosis leads to weakness, nausea, and vomiting. Hypokalemia causes muscle weakness, paralysis, abdominal distension and fullness, constipation, and dull heart sounds. Poor renal concentrating ability results in polydipsia, polyuria, and even dehydration.

bubble_chart Auxiliary Examination

The urine contains amino acids and glucose, and often presents with tubular proteinuria. Blood tests reveal metabolic acidosis, hypophosphatemia, and hypokalemia. Generally, there is no azotemia. X-ray examinations show rickets and osteoporosis.

Other manifestations vary depending on the primary disease.

bubble_chart Treatment Measures

﹝Treatment﹞

(I) Disease Cause: Treat the primary disease. (II) Symptomatic Treatment

1. Alkaline Drugs: Refer to "Renal Tubular Acidosis." Generally, 5–10 mmol/kg per day is required. For severe potassium loss, supplement 2–4 mmol/kg of potassium per day. A 10% syrup of potassium citrate and sodium citrate can be used.
2. Supplementation of Phosphorus, Calcium, and Vitamin D: For hypophosphatemia, administer neutral phosphate orally, 0.5–5.0 g per day (formulation: Na₂HPO₄·H₂O 145 g, NaH₂PO₄·H₂O 18.2 g dissolved in 1 L of syrup), along with calcium supplements and vitamin D, 10,000–50,000 U per day. Monitor urinary calcium levels, which should not exceed 6 mg/kg to avoid vitamin D toxicity. Due to impaired renal concentrating function, dehydration and fever may occur, so adequate hydration is necessary.

bubble_chart Differentiation

(1) It should be differentiated from renal tubular acidosis. (2) Conduct disease cause diagnosis:

1. **Hereditary**: Seen in primary hereditary Fanconi syndrome; also secondary to cystinosis, hepatolenticular degeneration (Wilson's disease), oculocerebrorenal syndrome (Lowe syndrome), fructose intolerance, tyrosinemia, galactosemia, vitamin D-dependent rickets, etc.
2. **Acquired**: Multiple myeloma, amyloidosis, Sjögren's syndrome, nephrotic syndrome, kidney transplantation, vitamin D deficiency, hyperparathyroidism, renal vein thrombosis in infants, liver tumors, potassium deficiency, interstitial nephritis (with anti-tubular basement membrane antibodies), etc. 3. **Toxicity**: Heavy metals such as mercury, lead, copper, cadmium, uranium, etc.; chemical substances including Lysol, salicylates, nitrobenzene, maleic acid, methyl-3-chromium, expired tetracycline, etc.