Definition - one of a group of muscle diseases that interfere with the processing of fats for energy production

Cause - either a defect in a gene for a protein, such as the carnitine transporter OCTN2, that brings carnitine into the cell ("primary" carnitine deficiency); or a deficiency of carnitine secondary to other metabolic diseases ("secondary" carnitine deficiency)

Onset -  infancy to early adulthood

Symptoms - if confined to muscles, weakness in the hips, shoulders, and upper arms and legs; face and tongue muscles may also be weak; heart muscle weakness may occur; in more severe cases, in which other tissues are affected, also includes low blood sugar, fatigue, vomiting, abdominal pain, growth retardation, low weight, enlarged liver, episodes of brain function abnormalities

Progression - usually slowly progressive

Inheritance - primary carnitine deficiency usually autosomal recessive, meaning caused by the contribution of a defective gene from each parent; secondary carnitine deficiency inheritance depends on primary cause

Facts About Metabolic Diseases of Muscle