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Editor,—Hoffman and Naughten rightly raise awareness for the potential misdiagnosis of the inherited metabolic disorder glutaric aciduria type I (GA-I) for the shaken baby syndrome, with its attendant psychosocial trauma to the family.1
When considering the diagnosis, particularly when there is no convincing history of significant trauma, they advocate the evaluation of urinary organic acids and serum carnitine to exclude GA-I.1 The typical urinary metabolites glutaric and 3-hydroxyglutaric acids may be present in the urine only intermittently, or not at all in non-excretors, irrespective of residual enzyme activity, even at times of decompensation.2 If strongly suspected, glutaryl-CoA dehydrogenase activity in cultured skin fibroblasts should be measured to avoid missing this important diagnosis.2 3
Misdiagnosis might not only expose the family to the risk of false accusation of child abuse, but may have disastrous consequences for the child. GA-I is a potentially treatable condition if diagnosed when neurodevelopment is normal, before metabolic decompensation, which characteristically leaves a severe, irreversible, dystonic movement disorder. Aggressive treatment of intercurrent infections, the institution of hyperalimentation during catabolic crises, with long term dietary protein restriction and carnitine supplementation may avoid decompensation4 and therefore avoid striatal damage. Confirmation of the diagnosis additionally allows the possibility of prenatal diagnosis and early treatment of affected siblings. The true potential for prevention of neurological sequelae requires evaluation following the introduction of national neonatal screening for this condition by tandem mass spectrometry, but for the present every effort should be made to obtain the diagnosis, and must include enzymology on cultured skin fibroblasts.
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