Methylmalonic acidemia, also called methylmalonic aciduria, is an autosomal recessive metabolic disorder that disrupts normal amino acid metabolism. It is a classical type of organic acidemia. The result of this condition is the inability to properly digest specific fats and proteins, which in turn leads to a buildup of a toxic level of methylmalonic acid in the blood.Methylmalonic acidemia stems from several genotypes, all forms of the disorder usually diagnosed in the early neonatal period, presenting progressive encephalopathy, and secondary hyperammonemia. The disorder can result in death if undiagnosed or left untreated. It is estimated that this disorder has a frequency of 1 in 48,000 births, though the high mortality rate in diagnosed cases make exact determination difficult. Methylmalonic acidemias are found with an equal frequency across ethnic boundaries. Symptoms and signs
Depending on the affected gene(s), this disorder may present symptoms that range from mild to life-threatening. Stroke
Progressive encephalopathy
Seizure
Kidney failure
Vomiting
Dehydration
Failure to thrive and developmental delays
Lethargy
Repeated yeast infections
Acidosis
Hepatomegaly
Hypotonia
Pancreatitis
Respiratory distress

Cause
Genetic
The inherited forms of methylmalonic acidemia cause defects in the metabolic pathway where methylmalonyl-coenzyme A (CoA) is converted into succinyl-CoA by the enzyme methylmalonyl-CoA mutase.Vitamin B12 is also needed for the conversion of methylmalonyl-CoA to succinyl-CoA. Mutations leading to defects in vitamin B12 metabolism or in its transport frequently result in the development of methylmalonic acidemia.This disorder has an autosomal recessive inheritance pattern, which means the defective gene is located on an autosome, and two copies of the gene—one from each parent—must be inherited to be affected by the disorder.
Though currently unclear if this is due to the specific mutation or early detection and treatment, despite complete nonresponse to cobalamin supplements, these individuals appeared to develop a largely benign and near completely asymptomatic version of MMA. Despite consistently showing elevated methylmalonic acid in the blood and urine, these individuals appeared for the large part developmentally normal. Notable cases
Ryan Stallings, a St. Louis infant, was mistakenly diagnosed with ethylene glycol poisoning instead of MMA in 1989, leading to a wrongful murder conviction and life sentence for his mother, Patricia Stallings. See also
Combined malonic and methylmalonic aciduria (CMAMMA)
Isovaleric acidemia
Propionic acidemia
Maple syrup urine disease

Notes
References
Further reading


== External links ==