Effect of chronic salt and water loading on the tubular defects of a child with Fanconi syndrome (cystinosis).

A male child discovered to have cystinosis and Fanconi syndrome at the age of 2 years 8 months was hospitalized repeatedly for episodes of hyponatremic, hypokalemic dehydration and acidosis. Attempts to correct the fluid and electrolyte abnormalities by increasing progressively the supplements of sodium chloride, sodium bicarbonate, and potassium chloride resulted only in an exacerbation of the symptoms. Tests of discrete renal functions and metabolic balance studies disclosed that, although all disturbances were expressions of the primary disease, their severity was enhanced considerably by the extracellular volume expansion induced by the vigorous therapy. Restriction in water intake resulted in an improvement in the renal performance and in the clinical condition.