An infant girl presented with recurrent episodes of
Reye-like syndrome associated with hypoketosis and plasma
carnitine levels in the high-normal range. A liver biopsy revealed massive macrovesicular steatosis. Ketogenesis was absent after a long-chain
triglyceride loading test; in contrast, the medium-chain
triglyceride loading test resulted in a brisk rise in plasma
ketone concentration.
Carnitine palmitoyltransferase I deficiency was demonstrated in cultured skin fibroblasts.
Hypoglycemia was only found once in the neonatal period. Renal
carnitine handling was normal except for a higher renal threshold for free
carnitine. Mild, persistent
metabolic acidosis was a constant feature, even during periods between metabolic decompensation. Evaluation of the renal acidification capacity showed a failure to acidify the urine during spontaneous
acidosis but increased
acid excretion and a normal decrease of urinary pH after
acid loading. Also, a small difference between urine and blood PCO2 was found after
bicarbonate administration. This acidification defect can best be explained as an abnormality in distal tubular H+ secretion: a rate-dependent distal tubular
acidosis.off is speculated that long-chain acylcarnitines, substances that cannot be formed by
carnitine palmitoyltransferase I-deficient patients, play an essential role in renal
acid-base homeostasis.