Overview Malonyl-CoA decarboxylase deficiency is a rare metabolic disorder that impairs the body’s ability to convert specific fats into usable energy. This condition generally presents its symptoms in early childhood. In nearly all cases, affected children experience developmental delays. Additionally, symptoms may include poor muscle tone (hypotonia), seizures, digestive issues such as diarrhea and vomiting, as well as episodes of low blood sugar (hypoglycemia). A notable complication is