Methylmalonic Acidemia (MMAB-Related) (MMAB)
Methylmalonic acidemia (MMAB-related) is a pan-ethnic, autosomal recessive disease caused by pathogenic variants in the MMAB gene. The most common presentation is during the newborn period, where a previously normal infant begins vomiting, and develops lethargy and hypotonia due to an excess of ammonia in the blood. Without immediate treatment, the resulting brain disease can be fatal. Patients can also present later in infancy or childhood after a period of normal development. Although the onset may be later, this form of the disease may also be fatal if not identified and treated promptly. Even with treatment, patients may develop intellectual disability, impaired function of the kidneys, vision loss, growth failure and pancreatitis. Life expectancy is variable depending on the number and length of metabolic crises and the severity of the resulting damage, but there is significant mortality associated with all ages. A clear genotype-phenotype correlation has not been reported.
For information about carrier frequency and residual risk, please see the residual risk table.