Fatty acid oxidation defects

Medium-chain acylCoA dehydrogenase (MCAD) deficiency

Clinical features:

Well babies or children who present with vomiting, lethargy proceeding to coma and liver disease in the course of an intercurrent illness such as gastroenteritis or with prolonged fasting. Some patients never have symptoms.

Laboratory tests:

Elevation of octanoyl carnitine is determined using tandem mass spectrometry. Follow-up tests include a DNA test, urine organic acids, and plasma acyl carnitines.

Treatment:

Avoidance of fasting, especially during intercurrent illness, when intravenous glucose may be needed.

Screening considerations:

Can be reliably detected unless the baby is already ill and carnitine-depleted at the time of the test.

Other fatty acid oxidation disorders.

Screening by tandem mass spectrometry can detect many of the fatty acid oxidation disorders including disorders of the carnitine cycle, and short chain and long chain disorders.

Clinical features:

The clinical features in untreated patients vary, and may involve liver disease, skeletal muscle and cardiac muscle disease.

Laboratory tests:

Measurement of several acyl carnitines are performed using tandem mass spectrometry. Follow-up tests may include a DNA test, urine organic acids, plasma acyl carnitines and a skin biopsy for analysis of relevant enzymes and/or metabolites.

Treatment:

Most of the disorders are treatable by dietary means and in one, carnitine medication is clearly indicated.

Screening considerations:

Reliability of detection for most disorders is not yet certain.