Methylmalonic acidemia is an inherited condition in which the body is unable to process certain proteins and fats properly. Signs and symptoms usually appear in early infancy and vary from mild to life-threatening. Affected infants can experience vomiting, dehydration, weak muscle tone (hypotonia), developmental delay, lethargy, hepatomegaly, and failure to thrive. Long-term complications can include feeding problems, intellectual disability, chronic kidney disease, and pancreatitis. Without treatment, this condition can lead to coma and death in some cases. Mutations in the MUT, MMAA, MMAB, MMADHC, and MCEE genes cause methylmalonic acidemia. It is inherited in an autosomal recessive fashion. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.