The clinical data of 14 patients with MMA admitted to our hospital between January 2002 and July 2003 were analyzed and the diagnoses were confirmed by gas chromatography/mass spectrometry (GC/MS). The patients consisted of 4 males and 10 females, whose age of onset ranged from birth to 9 years with 7 cases younger than 1 month (50%) and 10 cases younger than 1 year (71%).
RESULTS: The main clinical manifestations were
lethargy (6 cases), developmental retardation or regradation (7 cases), convulsion (6 cases), recurrent
vomiting (4 cases), difficulty with feeding (4 cases), muscular
dystonia (5 cases with
hypotonia, 3 with hypertonia) and yellowish hair (4 cases), etc. Some cases were also presented with
hair loss,
hepatomegaly, ataxic or stiff gait, and motor weakness with
muscular atrophy. The laboratory findings showed
metabolic acidosis in 6 cases,
hyperammonemia in 5 cases,
ketonuria in 4 cases and remarkable elevation of urinary
methylmalonic acid concentration in all cases. Some abnormalities in globus pallidus and cerebral white matter as well as diffuse cerebral
atrophy were noted by the brain CT and MRI in 5 respective cases, while 4 cases did not receive neuroradiological examinations.
Peripheral neuropathies were found by electromyography in 2 patients and bilateral optic nerve
atrophy was detected by eyeground examination in 1 child. Three patients died before the diagnoses were made. Of the 11 survivals, 10 children have received
therapy of
vitamin B12 (VitB12) and supplementation of
L-carnitine with restricted-
protein diet. The follow-up for a period ranging from 3 months to 1.5 year (mean 8.5 months) of 7 cases with medical
therapy showed a favorable outcome without any symptoms in 1 case and apparent improvement in 4 cases (the diffuse cerebral
atrophy in MRI completely recovered in one case), however, 2 patients died from severe
metabolic acidosis.
CONCLUSIONS: The main clinical features of MMA include
lethargy, developmental retardation or regradation, convulsion, recurrent
vomiting, difficulty with feeding, muscular
dystonia, yellowish hair,
metabolic acidosis,
hyperammonemia and
ketonuria, etc. Urine organic
acids analysis with GC/MS is critical to the early diagnosis of MMA. Early diagnosis and appropriate long-term treatment are essential to improve the prognosis of the disease.