Long-chain 3-hydroxyacyl-coenzyme A dehydrogenase (LCHAD) deficiency is a rare condition that prevents the body from converting certain fats to energy, particularly during periods without food (fasting). People with this disorder have inadequate levels of an enzyme that breaks down (metabolizes) a certain group of fats called long-chain fatty acids. Typically, initial signs and symptoms of this disorder occur during infancy or early childhood and can include feeding difficulties, lack of energy (lethargy), low blood sugar (hypoglycemia), muscle weakness (hypotonia), liver problems, and abnormalities in the part of the eye that detects light and color (retina). Muscle pain, a breakdown of muscle tissue, and abnormalities in the nervous system that affect arms and legs (peripheral neuropathy) may occur later in childhood. There is also a risk for complications such as life-threatening heart and breathing problems, coma, and sudden unexpected death. Episodes of LCHAD deficiency can be triggered by periods of fasting or by illnesses such as viral infections.