Summary of information
Methylmalonic acidurias (MMAurias) comprise a group of inborn errors of metabolism characterized by an isolated accumulation of methylmalonic acid (MMA) due to deficient activity of the enzyme methylmalonyl-CoA mutase.
Methylmalonic aciduria is a rare disorder and the true incidence in Europe is unknown. Estimates of incidence in Western populations range from 1:48,000 to 1:61,000 births, and overall incidence is believed to be ~ 1: 50,000.
Methylmalonic aciduria is caused by the deficient activity of methylmalonyl-CoA mutase (MCM), a vitamin B12 dependent mitochondrial enzyme which is essential for the catabolism of the amino acids threonine, methionine, isoleucine, valine, as well as cholesterol and odd-chain fatty acids.
The treatment of MMAuria is complex and requires regular monitoring and frequent therapeutic and dietary adjustments. It is recommended that the treatment and follow up of these patients be supervised by an experienced multidisciplinary team in a tertiary setting, although many aspects of care, including emergency management, can be delivered at the local or secondary level. Patients usually require 3-monthly follow up in order to monitor their clinical condition, nutritional status and growth and to make any changes to treatment as necessary. Long-term surveillance must include annual renal assessments to detect and manage renal impairment early and because of the potential for developing cardiac arrhythmias and cardiomyopathy in later life.