Progressive infantile neurodegeneration caused by 2-methyl-3-hydroxybutyryl-CoA dehydrogenase deficiency: a novel inborn error of branched-chain fatty acid and isoleucine metabolism.
We report a novel inborn error of metabolism identified in a child with an unusual neurodegenerative disease. The male patient was born at term and recovered well from a postnatal episode of metabolic decompensation and lactic acidosis. Psychomotor development in the first year of life was only moderately delayed. After 14 mo of age, there was progressive loss of mental and motor skills; at 2 years of age, he was severely retarded with marked restlessness, choreoathetoid movements, absence of directed hand movements, marked hypotonia and little reaction to external stimuli. Notable laboratory findings included marked elevations of urinary 2-methyl-3-hydroxybutyrate and tiglylglycine without elevation of 2-methylacetoacetate, mild elevations of lactate in CSF and blood, and a slightly abnormal acylcarnitine profile. These abnormalities became more apparent after isoleucine challenge. Enzyme studies showed absent activity of 2-methyl-3-hydroxybutyryl-CoA dehydrogenase (MHBD) in the mitochondrial oxidation of 2-methyl branched-chain fatty acids and isoleucine. Under dietary isoleucine restriction, neurologic symptoms stabilized over the next 7 months.
Zschocke
J
J
Division of Metabolic and Endocrine Diseases, University Children's Hospital, 69120 Heidelberg, Germany.
Ruiter
J P
JP
Brand
J
J
Lindner
M
M
Hoffmann
G F
GF
Wanders
R J
RJ
Mayatepek
E
E
D015094:3-Hydroxyacyl CoA Dehydrogenases; D000102:Acetyl-CoA C-Acyltransferase / Q000172:deficiency; D000429:Alcohol Oxidoreductases / Q000172:deficiency / Q000235:genetics* / Q000502:physiology; D000592:Amino Acid Metabolism, Inborn Errors / Q000178:diet therapy / Q000201:enzymology* / Q000235:genetics; D003937:Diagnosis, Differential; D018450:Disease Progression; D005227:Fatty Acids / Q000378:metabolism*; D006467:Hemophilia A / Q000150:complications / Q000235:genetics; D006801:Humans; D007231:Infant, Newborn; D008607:Intellectual Disability / Q000235:genetics; D007532:Isoleucine / Q000378:metabolism*; D008052:Lipid Metabolism, Inborn Errors / Q000178:diet therapy / Q000201:enzymology* / Q000235:genetics; D008297:Male; D008928:Mitochondria / Q000201:enzymology; D019636:Neurodegenerative Diseases / Q000150:complications / Q000201:enzymology / Q000235:genetics*; D010084:Oxidation-Reduction; D011595:Psychomotor Agitation / Q000209:etiology; D012640:Seizures / Q000209:etiology
D005227:Fatty Acids; D007532:Isoleucine; D000429:Alcohol Oxidoreductases; D015094:3-Hydroxyacyl CoA Dehydrogenases; C419903:2-methyl-3-hydroxybutyryl-coenzyme A dehydrogenase; D000102:Acetyl-CoA C-Acyltransferase