ABSTRACT
Most babies with inherited metabolic disease will be born at term and well at birth (Chakrapani et al., 2001). They become unwell after a clear asymptomatic interval of hours or days. Poor feeding, vomiting, dehydration (with weight loss of 10-15 per cent), encephalopathy or tachypnoea may be early signs. Encephalopathy may be characterized by periods of varying hypertonia or hypotonia or abnormal ‘cycling’ movements. Sustained hypertonia is characteristic of maple syrup urine disease (MSUD). There is hyperventilation in the absence of respiratory or cardiac abnormalities in severe acidosis and in hyperammonaemia, in which there may be a metabolic alkalosis. Hypoglycaemia may present subtly – poor feeding, apathy, pallor and sweating – or may present with convulsions. Liver failure may present as vomiting, bruising or bleeding (including intracranial bleeding) and jaundice. Always ask about consanguinity and ask about previous early neonatal deaths or illness, progressive or stepwise developmental delay or other neurological abnormality in other family members. A few disorders cause excretion of chemical intermediates that may impart an unusual smell to skin, urine or vomitus. The clinical features in acute metabolic disorders may be similar to those of sepsis: be prepared to reconsider presumed sepsis in a term baby with no risk factors for infection who does not respond to antibiotic therapy.
