Friedreich's ataxia: intravenous pyruvate load to demonstrate a defect in pyruvate metabolism.

Nine patients with typical Friedreich's ataxia had normal levels of pyruvate and lactate in blood, urine, and CSF. Glucose, pyruvate, and lactate levels were also within the reference ranges after oral glucose loading. After intravenous pyruvate loading, the relative increase in blood pyruvate and lactate levels was significantly higher in Friedreich's ataxia patients than in controls. Significant differences between the two groups were also observed in lactate-pyruvate ratios at various times after infusion. The pyruvate loading test can be useful in demonstrating a defect in pyruvate metabolism in Friedreich's ataxia patients.