FanconiSyndrom

Fanconi syndrome is a disorder of the proximal renal tubules characterized by a generalized defect in reabsorption. As a result, the kidneys lose glucose, amino acids, phosphate, bicarbonate and other solutes into the urine. Clinically, this causes glycosuria with normal blood glucose, aminoaciduria, phosphaturia, bicarbonaturia, and often a metabolic acidosis of proximal (type 2) renal tubular acidosis. Urinary loss of uric acid can also occur, leading to hypouricemia in serum.

Causes of Fanconi syndrome are divided into inherited and acquired categories. Inherited forms occur as part of broader conditions such as cystinosis or Lowe syndrome and are often evident in childhood. Acquired forms arise after exposure to nephrotoxins or drugs (for example cadmium or mercury exposure; cisplatin, ifosfamide, or certain antiretrovirals) and in association with other systemic diseases. The presentation and course depend on the underlying cause.

Clinical features include polyuria and polydipsia, dehydration, and, in children, growth retardation with rickets or osteomalacia due to phosphate wasting. Laboratory findings typical of the syndrome include metabolic acidosis with low bicarbonate, hypophosphatemia, glycosuria without hyperglycemia, aminoaciduria, and low-molecular-weight proteinuria.

Diagnosis is based on the combination of urinary losses of glucose, amino acids, phosphate and bicarbonate with preserved serum glucose and a compatible clinical context. Additional workup aims to identify the underlying cause and to assess electrolyte, acid–base status and bone health.

Treatment focuses on addressing the underlying cause, if possible, and correcting metabolic abnormalities. This may include bicarbonate therapy for acidosis, phosphate and vitamin D supplementation for bone disease, adequate hydration, and monitoring growth and development in children. The prognosis varies with the etiology and the extent of renal involvement.