Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

MMAP
31927
methylmalonyl-CoA mutase. Two other disorders (CblA and CblB) are associated with abnormalities in
the adenosylcobalamin synthesis pathway. CblC, CblD, and CblF deficiencies lead to impaired synthesis
of both adenosyl- and methyl-cobalamin. The final 2, CblE and CblG deficiencies, cause impaired
synthesis of the enzymes methionine synthase and methionine synthase reductase and are not associated
with abnormal MMA concentrations. Since the first reports of this disorder in 1967, many hundreds of
cases have been diagnosed worldwide. Newborn screening identifies approximately 1 in 30,000 live births
with a methylmalonic acidemia. The most frequent clinical manifestations are neonatal or infantile
metabolic ketoacidosis, failure to thrive, and developmental delay. Excessive protein intake may cause
life-threatening episodes of metabolic decompensation and remains a life-long risk unless treatment is
closely monitored, including serum and urine MMA levels. Because the morbidity and mortality of
methylmalonic acidemia are high, genetic counseling and prenatal diagnosis are frequently sought by
families with 1 or more affected children. The prenatal diagnosis is made on a dual, complementary
approach: enzymatic assays in cultured amniocytes or molecular analysis for previously identified familial
mutations and direct chemical determination of MMA in cell-free supernatant of amniotic fluid from
amniocentesis between 16 and 19 weeks of gestational age.
Useful For: Specific diagnostic marker for methylmalonic acidemia
Interpretation: A significantly increased amniotic fluid methylmalonic acid concentration supports
a diagnosis of methylmalonic acidemia
Reference Values: