Severe methylmalonic acidemia cblB type: a case report and literatures review
TONG Fan, YANG Ru-lai, WU Ding-wen, et al
TONG Fan, YANG Ru-lai, WU Ding-wen, HU Zhen-zhen, ZHANG Ting, ZHAO Zheng-yan (Department of Genetics and Metabolism, Children’s Hospital, Zhejiang University School of Medicine, Zhejiang, Hangzhou 310003, China
Abstract: Objective To investigate the phenotype and genotype characteristics, treatment and prognosis of methylmalonic acidemia (MMA) cblB type and to guide clinical diagnosis and treatment. Methods Clinical and biochemical features, treatment outcome and complications of one case of newborn with severe MMA cblB type found by newborn screening were retrospectively analyzed, and literatures were reviewed. Results The case showed high level of C3, increased ratio of C3/C2 and C3/C0, and high level of urine MMA in newborn screening testing. She had symptoms of failure to thrive and poor response during the neonatal period. The vitamin B12 loading test was negative. After feeding special formula, supplying L-carnitine and limiting protein intake, the clinical effect was not improved. The clinical manifestations were vomiting, failure to thrive, decreased peripheral blood leucocyte and hemoglobin, high level of lactic acid and blood ammonia with myocardial damage. She died at two-month-old. And genetic testing showed c.568C>T and c.563-577dup compound mutations in MMAB. Totally 53 cases of cblB were found in Chinese and PubMed database. The clinical symptoms varied from asymptom to severe metabolic decompensation, showed non-specific. The same genotype in one family may have different phenotype. MMAB gene was mainly on missense mutation, and 2 cases were c.568C>T among the 6 Asians. Conclusions The MMA cblB type has various and heterogeneous clinical symptoms. Early-onset type and severe type are common. It has the typical changes in biochemical markers of isolated MMA. The long-term treatments are mainly on feeding special formula, supplying L-carnitine, limiting protein and preventing acute attack. All the related genes should be detected for the patients with MMA.
2018, Vol. 6 
