Analysis of clinical data in 143 patients with methylmalonic acidemia

Objective Methylmalonic acidemia is a common inborn error of metabolism.According to the level of homocysteine,this disease can be classified into two types,isolated methylmalonic acidemia and methylmalonic acidemia combined with homocystinuria.The diagnosis of this disease is often delayed because of nonspecific clinical and laboratory findings.In this study,the clinical and biochemical features in patients with methylmalonic acidemia were analyzed,investigated and summarized,so as to help clinicians increase their awareness of this disease.Methods From 2003 to 2013,143 patients with methylmalonic acidemia were diagnosed and treated in our hospital.The clinical data of these patients were retrospectively analyzed,and the differences between patients of the two types were explored.Results Of the 143 patients,53 cases (37.1％) were suffering from isolated methylmalonic acidemia (isolated group) and 90 cases (62.9％) from combined methylmalonic acidemia with homocystinuria(combined group).The peak onset age in the isolated group ranged from 1 day to 1 month,and the common clinical and laboratory findings were recurrent vomiting,metabolic acidosis,and hyperammonemia.Among the combined group,the peak onset age was from 1 month to 1 year,and the most common clinical and laboratory findings were motor disorders and anemia.The levels of blood propionylcarnitine and its ratio with acetylcarnitine,and urine methylmalonic acid,13.54 (4.35-81.02) μmol/L,0.85 (0.38-2.89),and 632.08 (1 0.87-3 588.18) in the isolated group,and 7.97 (1.50-26.25) μmol/L,0.67 (0.28-2.06),and 161.04 (6.73-1 375.01) in the combined group,were respectively higher than those in healthy children (P＜0.01),and the differences in each parameter between the two types were statistically significant(P＜0.01).Conclusions Earlier onset and marked severity were seen in patients with isolated methylmalonic acidemia.Methylmalonic acidemia combined with homocystinuria was more common,and the clinical manifestation in the affected individuals was complex.Clinicians should pay attention to the utilization of MS/MS and GC-MS for screening the suspected patients,in order to achieve early diagnosis and early treatment. Key words: Methylmalonic acidemia ;  Tandem mass spectrometry ;  Gas chromatography-mass spectrometry;  Propionylcarnitine ;  Methylmalonic acid