Fanconi Syndrome
(more eponymous syndromes)

Renal Fanconi Syndrome is a medical condition arising from improper function of the proximal tubules of the kidney, resulting in a loss of metabolites and solutes in the urine. In a normally-functioning kidney, "useful" molecules in the urine, such as amino acids, sugars, phosphate and bicarbonate ion are reclaimed before the urine exits the kidney. This process is inhibited or absent in Fanconi Syndrome individuals. Signs of (hereditary) Fanconi Syndrome typically first appear in infants from 6 months to a year of age. Clinical indications include (obviously) presence of protein, amino acids, and other abnormal molecules in the urine, renal tubule acidosis, excessive thirst (polydipsia) and urination (polyuria), vomiting, anorexia and constipation.

Fanconi Syndrome can be caused by a number of external, non-hereditary factors such as kidney transplant, poisoning by expired antibiotics or heavy metals, or cancerous tumours, or it can be secondary to other disorders such as Wilson's disease (accumulation of copper in body tissues) or cystinosis. There are also hereditary cases, where the syndrome is passed on in an autosomal dominant manner. Recent research implicates a gene called HSPC129, which is homologous to a yeast gene (Psr2P) which codes for a protein which regulates sodium transport across the cell membrane. This suggests (to me, at least) that in many Fanconi cases, the transporters in the tubular walls are improperly down-regulated (hereditary) or irreversibly deactivated by binding of metal ions (metals poisoning or Wilson's Disease), leading to reduced transport of metabolites from the urine back into the kidney.

Zheng, F et al. (The clinical and biochemical manifestations of Fanconi syndrome: a report of 42 cases) Zhonghua Nei Ke Za Zhi. 2000 Nov;39(11):735-8. (Chinese w. English abstract, PubMed ID# 11798532)