What are the typical presenting symptoms of Fanconi syndrome?

Updated: Feb 09, 2018
  • Author: Sahar Fathallah-Shaykh, MD; Chief Editor: Craig B Langman, MD  more...
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Answer

The clinical features that cause patients to seek medical care include polyuria, polydipsia, bouts of dehydration (sometimes associated with fever), bone deformities, and impaired growth. Less often, the reasons for investigation are laboratory findings such as proteinuria, hypokalemia, hypophosphatemia, and hyperchloremic metabolic acidosis.

  • Polyuria, polydipsia, and dehydration are interrelated manifestations of the syndrome. They are primarily caused by the loss of excessive amounts of solutes in the urine, accompanied by the loss of water. Despite the dehydration that ensues, the urine is often dilute, which reflects a concentration defect that is partially caused by hypokalemia. The bouts of dehydration may be associated with fever, particularly in infants.

  • Rickets in children or osteomalacia in adults is the result of the excessive urinary losses of calcium and phosphate and of a defect in the hydroxylation of 25-hydroxyvitamin D3 into 1,25-dihydroxyvitamin D3.

  • Growth failure, a constant feature of the syndrome, is at least partially caused by the multiple metabolic abnormalities present in this condition. Prominent among these abnormalities are acidosis and disturbances in mineral and vitamin D metabolism. Yet, correction of these abnormalities fails to restore normal growth, particularly in patients with cystinosis.

  • Most patients have proteinuria, although it is often minimal. An obvious exception is the Fanconi syndrome that occurs in the context of nephrotic syndrome. The proteins may be of prerenal origin, as in multiple myeloma; of glomerular origin, as in advanced cases of cystinosis; or of tubular origin, as in all tubulopathies. The latter are the result of impaired reabsorption of small proteins, such as enzymes, peptide hormones, and light chain immunoglobulins. Their molecular weight varies from 5-50 kd.


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