Which presentation is most typical for infants with inborn errors of metabolism at birth?

• A. Dysmorphisms
• B. Non-specific clinical findings such as feeding problems or respiratory distress
• C. Normal appearance
• D. Seizures

Answer: (D)

The key idea is that metabolic disorders that begin in the newborn period often disrupt brain energy and lead to neurologic dysfunction, with seizures being a prominent and recognizable manifestation. When a newborn’s metabolism fails to provide the brain with its necessary substrates or when toxic metabolites build up, neuronal excitability increases and seizures can occur early and prominently. This CNS involvement is a common, high-yield clue to an inborn error of metabolism in the neonatal period.

Dysmorphic features can occur with certain metabolic or genetic conditions, but they are not universal or reliably present at birth for most IEM. A baby may look normal at birth or only show non-specific signs, so seizures stand out as a more typical early presentation of many metabolic crises. Feeding difficulties or respiratory distress are indeed common in many ill neonates, but seizures specifically reflect acute CNS metabolic disturbance, making them the most characteristic presentation in this context.

In practice, a newborn presenting with seizures should prompt consideration of an inborn error of metabolism and rapid metabolic evaluation, alongside supportive care to prevent catabolic stress and further neurologic injury.