title: Rate-dependent distal renal tubular acidosis and carnitine palmitoyltransferase I deficiency.
abstract: 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.
authors.affiliation: Department of Metabolic Diseases, University Children's Hospital, Het Wilhelmina Kinderziekenhuis, Utrecht, The Netherlands.
authors.forename: A J
authors.initials: AJ
authors.lastname: Bergman
authors.forename: R A
authors.initials: RA
authors.lastname: Donckerwolcke
authors.forename: M
authors.initials: M
authors.lastname: Duran
authors.forename: J A
authors.initials: JA
authors.lastname: Smeitink
authors.forename: B
authors.initials: B
authors.lastname: Mousson
authors.forename: C
authors.initials: C
authors.lastname: Vianey-Saban
authors.forename: B T
authors.initials: BT
authors.lastname: Poll-The
mesh_terms: D000141:Acidosis, Renal Tubular / Q000097:blood / Q000201:enzymology*; D001692:Biological Transport / Q000502:physiology; D002331:Carnitine / Q000097:blood*; D002334:Carnitine O-Palmitoyltransferase / Q000172:deficiency*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007231:Infant, Newborn; D007677:Kidney Function Tests; D011522:Protons; D012202:Reye Syndrome / Q000097:blood / Q000201:enzymology*; D012636:Secretory Rate / Q000502:physiology; D017693:Sodium Bicarbonate / Q000378:metabolism
chemical_list: D011522:Protons; D017693:Sodium Bicarbonate; D002334:Carnitine O-Palmitoyltransferase; D002331:Carnitine