Objective: To summarize the clinical characteristics

laboratory examinmation and gene of single or complicated methylmalonic acidemia (MMA) in our hospital by screening and follow-up from 2017 to now. Methods: The clinical manifestations

biochemical features and treatment were collected and analyzed. C3

C3/C2

methylmalonic acid

homocysteine

blood ammonia lactate

blood analysis and gene nucleotide results in the initial tandem mass spectrometry (MS/MS) were analyzed. Results: The most common clinical manifestations of MMA were feeding difficulty

weakness

seizure

hypoevolutism and so on. The longer interval from morbidity to treatment is

the poorer prognosis is. Laboratory findings showed that main laboratory examinations were hyperammonemia (6 cases

42.9%)

anemia (5 cases

35.7%)

granulocytopenia (7 cases

50%)

thrombocytopenia (5 cases

35.7%) and high-level homocysteine (63.6%). All single MMA patients had hyperammonemia. Compared with combined MMA patients

the level of C3 and urinary methylmalonic acid were increased and C3/C2 was lower

without statistically significant difference. Missense mutations was the main mutation in gene nucleotide changes

followed by insertions/deletions and duplications. MRI/CT results of 12 patients showed that brain atrophy (7 cases)

brain edema (4 cases) and delayed myelination (1 case); ultrasonic results of two patients showed slightly widened ventricles. Conclusion: Patients’clinical manifestation and laboratory examination lack of specificity in methacrylic acid. Tandem mass spectrometry and urine organic acids can be used for initial diagnosis

and the gene should be diagnosed and treated as soon as possible.