Vitamin B12-unresponsive methylmalonic acidemia type mut- is an inborn error of metabolism characterized by recurrent ketoacidotic comas or transient vomiting, dehydration, hypotonia and intellectual deficit, which does not respond to administration of vitamin B12. The disease is vitamin B12-unresponsive methylmalonic acidemia type mut- (Monarch Disease Ontology entry MONDO_0019267). Also known as: partial deficiency of methylmalonyl-CoA mutase, vitamin B12-unresponsive methylmalonic aciduria type mut-.