Very long-chain acyl-CoA dehydrogenase deficiency

Very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency is a condition that prevents the body from converting certain fats into energy, particularly during periods without food (fasting).

There are three forms of VLCAD deficiency, and they are defined by when the signs and symptoms of the condition begin. The early-onset form is the most severe and begins in infancy. Signs and symptoms can include lack of energy (lethargy) and muscle weakness. People with VCLAD deficiency can have low blood sugar (glucose), known as hypoglycemia. Affected individuals are also at risk for serious complications such, as liver abnormalities and life-threatening heart problems. 

Individuals with childhood-onset VLCAD deficiency typically experience an enlarged liver (hepatomegaly) and low blood glucose. This form is sometimes referred to as the hepatic or hypoketotic hypoglycemic form because of these signs. Additional signs and symptoms include other liver problems or muscle weakness.

The adult-onset form, which begins in adolescence or adulthood, usually involves muscle pain and the breakdown of muscle tissue (rhabdomyolysis). The destruction of muscle tissue releases a large amount of a protein called myoglobin, which is processed by the kidneys and released in the urine (myoglobinuria). Myoglobinuria causes the urine to be red or brown.

In both children and adults, problems related to VLCAD deficiency can be triggered by periods of fasting, illness, exercise, and exposure to hot or cold temperatures. In children, this disorder is sometimes mistaken for Reye syndrome, a severe disorder that may develop in children while they appear to be recovering from viral infections such as chicken pox or flu. Most cases of Reye syndrome occur in children who take aspirin during these viral infections.