Combined malonic and methylmalonic aciduria (CMAMMA) is an inborn error of metabolism characterized by elevations of urinary malonic acid (MA) and methylmalonic acid (MMA), MA elevations higher than MMA, and normal malonyl-CoA decarboxylase enzyme activity. The symptoms of CMAMMA are variable with presentation in childhood and in adults. Most patients have metabolic acidosis, developmental delay, seizures and cardiomyopathy; some affected individuals exhibit no clinical symptoms. Other findings reported include: coma, hypoglycemia, failure to thrive, immunodeficiency, microcephaly, dystonia reported in children, whereas adults have also presented with psychiatric disease, memory problems and cognitive decline. The incidence of CMAMMA has been estimated at approximately 1 in 30,000.