Fanconi syndrome

Fanconi syndrome or Fanconi's syndrome (fɑːnˈkoʊni, fæn-) is a syndrome of inadequate reabsorption in the proximal renal tubules of the kidney. The syndrome can be caused by various underlying congenital or acquired diseases, by toxicity (for example, from toxic heavy metals), or by adverse drug reactions. It results in various small molecules of metabolism being passed into the urine instead of being reabsorbed from the tubular fluid (for example, glucose, amino acids, uric acid, phosphate, and bicarbonate). Fanconi syndrome affects the proximal tubules, namely, the proximal convoluted tubule (PCT), which is the first part of the tubule to process fluid after it is filtered through the glomerulus, and the proximal straight tubule (pars recta), which leads to the descending limb of loop of Henle. Different forms of Fanconi syndrome can affect different functions of the proximal tubule, and result in different complications. The loss of bicarbonate results in type 2 or proximal renal tubular acidosis. The loss of phosphate results in the bone diseases rickets and osteomalacia (even with adequate vitamin D and calcium levels), because phosphate is necessary for bone development in children and even for ongoing bone metabolism in adults. renal tubular acidosis The clinical features of proximal renal tubular acidosis are: Polyuria, polydipsia and dehydration Hypophosphatemic rickets (in children) and osteomalacia (in adults) Growth failure Acidosis Hypokalemia Hyperchloremia Other features of the generalized proximal tubular dysfunction of the Fanconi syndrome are: Hypophosphatemia/hyperphosphaturia Glycosuria Proteinuria/aminoaciduria Hyperuricosuria In contrast to Hartnup disease and related tubular conditions, Fanconi syndrome affects the transport of many different substances, so is not considered to be a defect in a specific channel, but a more general defect in the function of the proximal tubules. Different diseases underlie Fanconi syndrome; they can be inherited, congenital, or acquired.