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Inherited metabolic disease

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A. Awadalla, E. Treacy, A. Monavari, E. Crushell, S. Harty.Children’s University Hospital, Dublin, Ireland

Aims: Inborn errors of metabolism are reported to be a rare cause (1–5%) (Shevell et al) of developmental delay. The aims are to determine the aetiological yield of metabolic investigation in children referred to a tertiary metabolic service where developmental delay was a primary feature, and to determine the variables that make achieving a diagnosis more likely.

Methods: Cases were identified retrospectively from the database at the national centre for inborn errors of metabolism and details obtained from case notes. Referral information, history, examination findings, investigations and diagnosis were studied.

Results: Fifty two cases (31 male, 21 female, and age range 7–175 months) were identified between January 2004 and December 2005. Source of referral were General Paediatrician (33), Paediatric Neurologist (14), General Practitioner (2) and others (3). 13 (25%) patients had a definitive metabolic diagnosis, including 5 (9.6%) that had a diagnosis at referral. A metabolic diagnosis was strongly suspected in a further 6 patients. Definitive diagnoses included: mitochondrial disorder (9), SCAD (1), SCHAD (1), EMA encephalopathy (1), Orotic aciduria (1). Three additional patients were found to have other genetic disorders. Children with a definitive metabolic diagnosis were compared with those in whom no diagnosis was found. Abnormal eye examination (30.7% v 15.6%), microcephaly (25% v 13.7%), seizures (23% v 10%) and referral by a paediatric neurologist (50% v 25.9%) were more likely in patients with a definitive diagnosis. Biochemical markers positively associated with a definitive diagnosis included a high serum lactate (30.7% v 15.6%), abnormal serum amino acids (69.2% v 33.3%) and abnormal urine organic acids (61.5% v 12%). Patients with autistic features were less likely to have a metabolic diagnosis (15% v 34.4%).

Conclusion: The aetiological yield of metabolic testing is significantly higher …

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