[Diagnosis and treatment of isolated methylmalonic acidemia].
OBJECTIVE
To explore the clinical feature, therapeutic effect and prognosis of isolated methylmalonic acidemia.


METHODS
The clinical characteristics, laboratory findings, treatment and outcome of 40 patients were retrospectively analyzed. The main treatment was a low-protein diet supplemented with L-carnitine and special milk free of leucine, valine, threonine and methionine. Vitamin B12 was also given to cobalamin responders. The patients were followed up every 1-3 months.


RESULTS
Mutations in the MUT gene were identified in 30 of 33 patients who had accepted DNA testing. Thirty cases were treated and followed up regularly for from 1 month to 8 years. Eight cases had died, 8 had developed normal intelligence, among whom 4 from newborn screening were asymptomatic. Psychomotor developmental delay and mental retardation were present in 14 cases. The propionylcarnitine level, ratio of propionylcarnitine/acetylcarnitine in blood, methylmalonic acid and methylcitric acid levels in urine have decreased significantly, with the median values reduced respectively from 24.15 (7.92-81.02) μmol/L, 1.08 (0.38-6.01), 705.34 (113.79-3078.60) and 7.71 (0.52-128.21) to 10.50 (3.00-30.92) μmol/L, 0.63 (0.25-2.89), 166.23 (22.40-3322.21) and 3.96 (0.94-119.13) (P < 0.05).


CONCLUSIONS
The prognosis of isolated methylmalonic acidemia may be predicted with the enzymatic subgroup, age at onset and cobalamin responsiveness. Outcome is unfavorable in neonatal patients and those who were non-responsive to cobalamin.
Department of Pediatric Endocrinology, Genetic and Metabolic Diseases, Shanghai Institute of Pediatric Research, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 210092, P. R. China. Email: gu_xuefan@163.com.
Lian-shu
LS
Han
Sheng-nan
SN
Wu
Jun
J
Ye
Wen-juan
WJ
Qiu
Hui-wen
HW
Zhang
Xiao-lan
XL
Gao
Yu
Y
Wang
Xiao-yan
XY
Li
Hao
H
Xu
Xue-fan
XF
Gu
D000592:Amino Acid Metabolism, Inborn Errors / Q000175:diagnosis* / Q000178:diet therapy* / Q000201:enzymology / Q000378:metabolism; D002331:Carnitine / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D018753:Diet, Protein-Restricted / Q000706:statistics & numerical data; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008765:Methylmalonyl-CoA Mutase / Q000235:genetics; D012189:Retrospective Studies
D008765:Methylmalonyl-CoA Mutase; D002331:Carnitine