Fanconi syndrome

Fanconi syndrome (Fanconi’s syndrome) is a disease of the proximal renal tubules of the kidney.

The proximal tubules of the kidney allow glucose, amino acids, uric acid, phosphate and bicarbonate to pass into the urine, instead of being reabsorbed.

The FS may be inherited, or caused by drugs or heavy metals.

Different forms of Fanconi syndrome can affect different functions of the proximal tubule.

Different affects on the proximal tubule result in different complications: The loss of bicarbonate results in type 2 or proximal renal tubular acidosis, The loss of phosphate results in rickets because phosphate is necessary for bone development.

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/phosphaturia
Glycosuria

Proteinuria/aminoaciduria

Hyperuricosuria

Affects the transport of many different substances, so it is a more general defect in the function of the proximal tubules.

Can be inherited, congenital, or acquired.

Cystinosis is the most common cause in children.

Other causes are Wilson’s disease, Lowe syndrome, tyrosinemia (type I), galactosemia, glycogen storage diseases, and hereditary fructose intolerance.

Dent’s disease and Lowe syndrome, are X linked.

Acquired disease includes: ingestion of expired tetracyclines, side effect of tenofovir in cases of pre-existing renal impairment, tenofovir and didanosine exposure, and lead poisoning.

Associated with Multiple myeloma or Monoclonal gammopathy of undetermined significance.

Treatment of children with Fanconi syndrome consists of replacement of substances lost in the urine such as fluids and bicarbonate.

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