Organic acidopathies

A range of these disorders may be detected, including those mentioned below.

Clinical features:

Methylmalonic aciduria, propionic acidaemia and isovaleric acidaemia may present with severe metabolic acidosis in the newborn period or later. A more insidious presentation is also possible. Several other even rarer disorders can also present in this way. Glutaric aciduria type I can present during an intercurrent illness with severe dystonia (abnormal movements) of sudden onset, or may present insidiously with hypotonia and milder dystonia. There is usually macrocephaly (a large head).

Laboratory tests:

Detection of a range of acyl carnitines is performed using tandem mass spectrometry. Follow-up tests include urine organic acids and plasma acylcarnitines.

Treatment:

Often a low protein diet is needed, plus specific medications in some of the disorders. Carnitine supplementation is helpful in many of the disorders.

Screening considerations:

Reliability of detection is not known, but should be high for most organic acidopathies. For glutaric aciduria type I, a proportion of patients are "low excretors" and detection may be difficult or impossible.