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Methylmalonic Acidemia

  • MUT, MMAA and MMAB genes
Methylmalonic acidemia is a family of autosomal recessive disorders characterized by deficient activity of mitochondrial methylmalonyl-CoA mutase. This inborn error of organic acid metabolism leads to defects in organic acid, amino acid and lipid metabolism. Patients have a characteristic facies that includes a high forehead, broad nasal bridge and a long, smooth filtrum. Affected infants often have recurrence of acute illness with metabolic acidosis, vomiting, failure to thrive, lethargy, hypotonia, hepatomegaly, seizures and respiratory distress. The most severe clinical presentation is in the neonatal period and can result in death. The disorder may also have a later onset, in the first months or years and, less commonly, in early childhood. An adult form can have a benign course with a mild biochemical defect; however these individuals are at risk for acute metabolic decompensation. Complications of methylmalonic acidemia include mental retardation, nephritis, chronic renal tubular acidosis, metabolic stroke, pancreatitis, growth failure and functional immune impairment.

Using genomic DNA obtained from buccal swabs (not accepted on infants) or blood (2mL for infants, 5mL for adults in EDTA), mutation analysis of the MUT gene is performed. GeneDx offers the option of first testing for the common MUT mutation in exon 2 (c.322C>T) that is found in up to 60% of patients of Hispanic descent and is homozygous in approximately 20% of patients. If homozygosity for this mutation is not observed or the patient is not of Hispanic decent, the entire coding sequence and intron/exon boundaries of the MUT, MMAA, and MMAB genes can be ordered individually or simultaneously in any order. However, mutations in the MUT gene are most common. Carrier testing and prenatal diagnosis is available once the mutation in the family has been defined.

Information Sheet, including prices and CPT codes Back to the List
Consent Document  
Genetic Test Sample Submission Form (Test Requisition Form) including Payment Options  
MMA, MCM deficiency, mut Type, mut(0) Type, mut(-) type, MCM, methylmalonyl-CoA isomerase, cobalamine adenosyltransferase, adenosylcobalamin, vitamin B12

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