Enzymologic studies on patients with methylmalonic aciduria: basis for a clinical trial of deoxyadenosylcobalamin in a hydroxocobalamin-unresponsive patient.
Eleven patients with methylmalonic aciduria have been classified on the basis of detailed enzymology on cultured skin fibroblasts. Nine were classified as mutase deficiencies and were unresponsive to hydroxocobalamin in vivo or in vitro. One was classified as a Cbl A variant and was responsive to hydroxocobalamin therapy in vitro and in vivo. Patient 11 was classified as having deoxyadenosyltransferase deficiency (Cbl B). However, a clinical therapeutic trial of deoxyadenosylcobalamin resulted in no clinical or biochemical improvement. Further studies on the patient's cultured fibroblasts suggested that deoxyadenosylcobalamin fails to reach the mitochondria in an intact form. These studies show that detailed enzymologic classification is essential for the reliable evaluation of the response to therapeutic maneuvers; complementation studies alone may be inadequate to completely classify these patients. Therapy with deoxyadenosylcobalamin offers no advantages over the use of hydroxocobalamin in the treatment of patients with methylmalonic aciduria.
Department of Child Health, St. George's Hospital Medical School, London, United Kingdom.
R A
RA
Chalmers
M D
MD
Bain
J
J
Mistry
B M
BM
Tracey
C
C
Weaver
D019883:Alkyl and Aryl Transferases; D002460:Cell Line; D003038:Cobamides / Q000627:therapeutic use*; D005260:Female; D005347:Fibroblasts / Q000201:enzymology; D006801:Humans; D006879:Hydroxocobalamin / Q000627:therapeutic use; D007223:Infant; D008764:Methylmalonic Acid / Q000652:urine*; D008765:Methylmalonyl-CoA Mutase / Q000172:deficiency; D014166:Transferases / Q000172:deficiency
D003038:Cobamides; D008764:Methylmalonic Acid; D014166:Transferases; D019883:Alkyl and Aryl Transferases; C019920:cob(I)alamin adenosyltransferase; D008765:Methylmalonyl-CoA Mutase; C000913:cobamamide; D006879:Hydroxocobalamin