Medical Care
The treatment of a child with Fanconi syndrome mainly consists of the replacement of substances lost in the urine. Prominent among these substances are fluids and electrolytes.
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Dehydration due to polyuria must be prevented by allowing free access to water; treat dehydration with either oral or parenteral solutions.
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Metabolic acidosis due to the loss of bicarbonate is corrected by the administration of alkali, usually 3-10 mg/kg/d of sodium bicarbonate in divided doses.
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Addition of a diuretic, such as 1-3 mg/kg/d of hydrochlorothiazide, may be necessary to avoid volume expansion, which magnifies the excretion of bicarbonate by lowering the renal threshold. Unfortunately, the diuretic increases potassium wasting and thus the need to augment potassium supplementation in the form of potassium bicarbonate, citrate, or acetate.
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Correction of metabolic acidosis is beneficial but is not sufficient for the treatment of bone disease. Phosphate and vitamin D supplementation are also necessary.
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Normalization of serum phosphate levels may be achieved by administering 1-3 g/d of supplemental phosphate. Administration should start at the lower level and be slowly increased over several weeks to minimize GI symptoms.
Vitamin D, administered as 1,25-dihydroxyvitamin D3 or 1a-hydroxyvitamin D3, is preferred because liver and/or renal hydroxylation may be impaired in patients with Fanconi syndrome.
The losses of glucose, amino acids, and uric acid are not usually symptomatic and do not require replacement. Recently, carnitine supplementation has been tried in an attempt to increase muscle strength; however, results have been mixed.
Monitoring
Closely monitor all patients with Fanconi syndrome, independent of etiology or pathogenesis. Frequency of the patient's visits depends on various factors, including the severity of the syndrome, the ability to maintain fluid and electrolyte balance, the degree of involvement of other organs, and the need for monitoring the effects and side effects of specific medications.
Surgical Care
Liver transplantation has been successfully used in patients with liver failure due to Wilson disease or tyrosinemia. Liver transplantation leads to the rapid disappearance of the renal tubular abnormalities.
Kidney transplantation has been performed in many patients with renal failure due to cystinosis. Cystine accumulates in the monocytes and interstitial cells of the transplanted kidney but not in proximal tubule cells. Consequently, the tubular transport abnormalities do not recur.
Consultations
A slit-lamp eye examination should be requested whenever the diagnosis of cystinosis is suspected. Detection of needle-shaped refractile bodies in the cornea is pathognomonic. In patients with Wilson disease, a slit-lamp examination can be used to detect the pathognomonic Kayser-Fleischer rings. An ophthalmology consultation is also warranted in patients with galactosemia and Lowe syndrome because ocular manifestations can be present.
Diet and Activity
Diet
Several forms of Fanconi syndrome are caused by deficiencies in enzymes involved in the metabolism of nutrients, such as galactose, fructose, tyrosine, and phenylalanine. Elimination of these substances from the diet results in the disappearance of the renal manifestations of the syndrome. However, some of the systemic abnormalities, such as developmental delay, growth retardation, speech impairment, and ovarian dysfunction in galactosemia or hepatic cirrhosis in tyrosinemia, do not appear to be affected. Patients with Wilson disease benefit from a low-copper diet and therapy with D-penicillamine.
Activity
None of the conditions associated with Fanconi syndrome mandate restrictions in activities. However, some of these conditions can result in failure of organs, such as the liver or kidneys, or in diminution of muscle strength, which, in turn, may limit the ability of children to engage in physically demanding activities.
Prevention
Some of the secondary forms of Fanconi syndrome may be limited by preventing exposure to toxins such as lead and outdated tetracyclines and aminoglycosides. Eliminating lactose from the diet in children with galactosemia and tyrosine/phenylalanine from the diet in children with tyrosinemia helps alleviate the symptoms in some of the primary forms of Fanconi syndrome.
