A boy with methylmalonic aciduria - nine-year follow up and comparison with his healthy twin sister

Methylmalonic aciduria is a recessively inherited disorder of methylmalonate metabolism and one of the most common organic acidurias. Four distinct defects are known to cause isolated methyl-malonyl-CoA mutase deficiency. We present a boy whose two older brothers died in the neonatal period from septicemia. His twin sister is healthy. During the first day of life and then from 4 to 6 months of age, he had several episodes of metabolic decompensation provoked by infection, diarrhea and fasting. Hyperlactacidemia, mild ketonuria, hyperammonemia, anemia, low values of total and free carnitine in plasma and urine were found. Urinary organic acid analysis showed high excretion of methylmalonic, 3-OH butyric, 3-OH propionic and methylcitric acids. Serum cobalamin and folic acid were normal. The activities of holomutase and total mutase in fibroblasts were severely decreased indicating a defect of MCM apoenzyme (mut0). After the diagnosis at the age of 6 months, a low protein diet was introduced with natural proteins and amino acid supplement; L-carnitine, B12 vitamin, folate, vitamins and alternating prophylactic antibiotics were given. From infancy, motor and growth delay was evident in comparison to his twin sister. Because of low compliance of the patient’s parents ignoring the feeding instructions and infections, he had frequent metabolic crises and decompensations, which resulted in growth delay, and at the age of 9 years his twin sister was 25 cm taller (his body height was at -3 SD). The long-term prognosis of patients with MMA mut0 is very poor. Early diagnosis and progress in treatment will reduce mortality and morbidity of patients with methylmalonic aciduria.

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