Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is a rare inherited metabolic disorder that impacts a baby’s ability to convert certain fats into energy. This prevents the body from properly breaking down medium-chain fatty acids, especially when sugar stores are low. Early detection and careful management are important for affected infants.
Understanding MCAD Deficiency
Inside the body’s cells, energy is produced as fats are broken down in the mitochondria, often called the “powerhouses of the cell.” For individuals with MCAD deficiency, a specific enzyme, medium-chain acyl-CoA dehydrogenase, is either missing or significantly reduced, preventing a key step in this fat breakdown process. This means the body cannot effectively convert medium-chain fatty acids into usable energy, especially during periods of fasting or illness when the body relies more heavily on fat stores. This inability to process fats leads to a buildup of harmful substances in the body, which can have serious consequences. The condition is inherited in an autosomal recessive pattern, meaning a baby must inherit a changed copy of the ACADM gene from each parent to develop the disorder.
Recognizing Signs in Babies
Babies with MCAD deficiency appear healthy at birth, and symptoms may not become apparent until later, often between 1 month and 2 years of age. Symptoms usually emerge during periods of prolonged fasting, such as extended sleep or missed feedings, or during illnesses like fevers or common colds, when the body’s energy demands increase.
Common signs of a metabolic crisis in babies can include lethargy, vomiting, and dangerously low blood sugar, known as hypoglycemia. Other symptoms may involve liver problems, such as an enlarged liver, and muscle weakness. These symptoms can vary in severity and may not be specific to MCAD deficiency, making early recognition challenging without newborn screening. Untreated severe hypoglycemic episodes can lead to seizures, coma, and in some cases, can be fatal.
Diagnosis and Initial Treatment
MCAD deficiency is most commonly identified in the first few days of life through newborn screening programs. In the United States, all states routinely test for MCAD deficiency at birth using a heel prick to collect a few drops of the baby’s blood for analysis. If screening results are outside the typical range, additional testing is performed to confirm the diagnosis.
Confirmatory diagnostic tests may include biochemical testing, such as an acylcarnitine profile, and DNA testing to identify specific genetic changes in the ACADM gene. If a metabolic crisis is suspected or diagnosed, immediate medical intervention involves administering intravenous glucose-containing fluids to raise blood sugar levels and prevent further fat breakdown.
Living with MCAD Deficiency
Managing MCAD deficiency involves strategies aimed at preventing metabolic crises and maintaining stable energy levels. A primary focus is avoiding prolonged fasting, which means ensuring frequent feedings for infants to prevent their blood sugar from dropping too low. This often requires parents to follow strict feeding schedules.
Dietary modifications are also important, which may include a diet higher in carbohydrates and lower in fats than typically recommended. Some babies may require special formulas. Close monitoring by a metabolic specialist is necessary to adjust treatment plans as the child grows and their energy needs change. For individuals diagnosed and managed early, the prognosis is favorable, allowing them to lead healthy lives. Families are also encouraged to have a detailed emergency plan for managing illness or unexpected situations.