The symptoms of propionic acidemia, an autosomal recessive disorder involving deficiency of the enzyme propionyl-coenzyme A carboxylase, are highly varied and may present at any time in the patient's life. Cardiomyopathy, a rare complication of this disorder, has been reported in only a small number of pediatric patients. The authors describe a case of adult-onset cardiomyopathy in a 23-year-old female with propionic acidemia diagnosed in early childhood and associated with multiple long-standing comorbidities. The possible mechanisms of propionic acidemia-associated cardiomyopathy, and the importance of early recognition and appropriate management, are discussed. (c)2001 CHF, Inc.