title: [A Chinese boy with methylmalonic aciduria cblB type and a novel mutation in the MMAB gene].
abstract: cblB defect is a rare type of methylmalonic aciduria. In this study, a Chinese boy was diagnosed with methylmalonic aciduria cblB type and a novel mutation in the MMAB gene. The clinical presentations, blood acylcarnitines profiles, urine organic acids and genetic features of the patient were reported. The boy presented with fever, feeding difficulty and lethargy at the age of 2 months. Seven days later, he had coma, cold limb, thrombocytopenia, metabolic acidosis and liver damage. His blood propionylcarnitine and urinary methylmalonic acid levels increased significantly, but the plasma total homocysteine level was in the normal range, which supported the diagnosis of isolated methylmalonic aciduria. Gene analysis was performed by direct sequencing. No mutation in the MUT gene was found. However, a reported mutation c.577G>A (p.E193K) and a novel mutation c.562G>A (p.V188M) in the MMAB gene were identified, which confirmed the diagnosis of methylmalonic aciduria cblB type. Progressive clinical and biochemical improvement has been observed after hydroxylcobalamin injection, protein-restricted diet with the supplements of special formula and L-carnitine. He is currently 3 years and 11 months old and has a normal development condition. The phenotypes of the patients with cblB defect are nonspecific. Metabolic analysis and MMAB gene analysis are keys for the diagnosis of the disorder.
authors.affiliation: Department of Pediatrics, Peking University First Hospital, Beijing 100034, China. organic.acid@126.com.
authors.forename: Yu-Peng
authors.initials: YP
authors.lastname: Liu
authors.forename: Hai-Jun
authors.initials: HJ
authors.lastname: Wang
authors.forename: Tong-Fei
authors.initials: TF
authors.lastname: Wu
authors.forename: Xi-Yuan
authors.initials: XY
authors.lastname: Li
authors.forename: Jin-Qing
authors.initials: JQ
authors.lastname: Song
authors.forename: Yuan
authors.initials: Y
authors.lastname: Ding
authors.forename: Yao
authors.initials: Y
authors.lastname: Zhang
authors.forename: Qiao
authors.initials: Q
authors.lastname: Wang
authors.forename: Yan-Ling
authors.initials: YL
authors.lastname: Yang
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics*; D000592:Amino Acid Metabolism, Inborn Errors / Q000235:genetics*; D006801:Humans; D007223:Infant; D008297:Male; D009154:Mutation
chemical_list: D019883:Alkyl and Aryl Transferases; C019920:cob(I)alamin adenosyltransferase