What is Fanconi syndrome?

Updated: Jun 19, 2020
  • Author: Horacio B Plotkin, MD, FAAP; Chief Editor: Jatinder Bhatia, MBBS, FAAP  more...
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Fanconi syndrome is a disorder of proximal renal tubular transport. Phosphate, amino acid, glucose, bicarbonate, and uric acid wasting characterize this disorder. Dysfunctions in tubular phosphate reabsorption via the sodium-phosphate cotransporter, endocytotic reabsorption of the vitamin D–vitamin D–binding protein complex mediated by megalin and cubilin, and acid-base regulation are the most important factors that cause bone mineralization defects in these patients. [7]

Lowe disease and Dent disease are familial forms of Fanconi. Two different genes have been identified as being involved in the development of Dent disease. CLCN5 is affected in Dent disease type 1 and OCRL1 is affected in Dent disease type 2. Other genes may also be involved, because mutations in CLCN5 and OCRL1 are not found in some patients.

In Fanconi syndrome, which includes cystinosis and tyrosinemia, renal phosphate wasting may occur, along with aminoaciduria and glycosuria.

Fanconi syndrome can have a genetic cause (as in Lowe and Dent disease), or it may be acquired from various toxins, including heavy metals (eg, mercury, lead) and drugs. The clinical picture varies with age and cause and includes severe hypophosphatemic rickets, failure to thrive, and metabolic acidosis.

A potential drug-induced Fanconi syndrome has been noticed in children treated with ifosfamide, a derivative of cyclophosphamide. The syndrome presents with radiologic changes compatible with rickets. Most patients respond to a combination of managing the underlying cause when possible and vitamin D therapy. These patients do not necessarily appear to require treatment with calcitriol. Renal tubular acidosis, through phosphate wasting, may also cause rickets.

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