MCAD deficiency in adults

MCAD (medium-chain acyl-CoA dehydrogenase) deficiency is an inherited metabolic condition affecting the body's ability to break down certain fats for energy, particularly during periods of fasting or illness. While usually identified through newborn screening, milder cases can occasionally present or persist into adulthood.

It's caused by mutations in the ACADM gene, which produces an enzyme needed to break down medium-chain fatty acids for energy, inherited in an autosomal recessive pattern. Without this enzyme working properly, the body struggles to access this energy source during fasting, relying more heavily on glucose.

In adults, symptoms can include episodes of low blood sugar, lethargy, or, in severe metabolic crises, more serious complications, typically triggered by prolonged fasting, illness, or significant physical exertion. Many adults with milder genetic variants remain asymptomatic as long as they avoid prolonged fasting.

Yes, during a metabolic crisis triggered by prolonged fasting or illness, low blood sugar and other complications can become serious or, rarely, life-threatening if not promptly recognised and treated. With appropriate awareness and management, particularly avoiding prolonged fasting, most complications can be prevented.

Yes, it's an inherited genetic condition, and genetic testing can confirm the diagnosis. Genetic counselling is recommended for affected individuals considering having children, given the autosomal recessive inheritance pattern.

Yes, the mainstay of management is avoiding prolonged periods without food, particularly during illness, and having a clear emergency plan for managing situations where normal eating isn't possible. With this careful management, most people with MCAD deficiency live healthy, normal lives.

Management centres on avoiding prolonged fasting, maintaining regular meals particularly during illness, and having a specific emergency management plan, sometimes including glucose supplementation, for situations of illness or reduced food intake. Ongoing specialist metabolic medicine input helps ensure this management remains appropriate over time.

Diagnosis is typically made through newborn screening in infancy, identifying a specific metabolic marker pattern, confirmed with genetic testing. Occasionally, milder cases are diagnosed later in life following investigation of an unexplained metabolic episode.

MCAD deficiency specifically affects the breakdown of medium-chain fatty acids and is generally one of the more common and often milder fatty acid oxidation disorders, whereas other related conditions affect different specific enzymes and fatty acid chain lengths, sometimes with more severe presentations. Specific genetic and metabolic testing distinguishes between these related but distinct inherited conditions.

A positive newborn screening result or unexplained episodes of low blood sugar with illness should prompt metabolic medicine assessment. Private specialist consultations can typically be arranged within about two weeks, though acute symptoms need urgent same-day medical attention.