Methylmalonic Acidemia: Diagnosis and Neuroimaging Findings of This Neurometabolic Disorder (An Iranian Pediatric Case Series)

OBJECTIVE: Methylmalonic acidemia is one of the inborn errors of metabolism resulting in the accumulation of acylcarnitine in blood and increased urinary methylmalonic acid excretion. This disorder can have symptoms, such as neurological and gastrointestinal manifestations, lethargy, and anorexia. MATERIALS & METHODS: The patients who were diagnosed as methylmalonic acidemia in the Neurology Department of Mofid Children’s Hospital in Tehran, Iran, between 2002 and 2012 were included in our study. The disorder was confirmed by clinical findings, neuroimaging findings, and neurometabolic and genetic assessment in reference laboratory in Germany. We assessed the age, gender, past medical history, developmental status, clinical manifestations, and neuroimaging findings of 20 patients with methylmalonic acidemia. RESULTS: Eighty percent of the patients were offspring of consanguineous marriages. Half of the patients had Failure to thrive (FTT) due to anorexia; 85% had history of developmental delay or regression, and 20% had refractory seizure, which all of them were controlled. The patients with methylmalonic acidemia were followed for approximately 5 years and the follow-up showed that the patients with early diagnosis had a more favorable clinical response in growth index, refractory seizure, anorexia, and neurodevelopmental delay. Neuroimaging findings included brain atrophy, basal ganglia involvement (often in putamen), and periventricular leukomalacia. CONCLUSION: According to the results of this study, we suggest that early assessment and diagnosis have an important role in the prevention of disease progression and clinical signs.