Presentation

In general, inborn errors of metabolism present in one of three ways:

• mild acidosis but raised ammonia, in urea cycle defects
• with severe acidosis and markedly raised ketones, in organic acidaemias
• with severe acidosis, profound hypoglycaemia, but only mild ketosis in problems with lipid and carbohydrate metabolism

The features are those of progressive unwellness with vomiting, lassitude and deterioration to convulsions, coma and eventually death. They may present in the few hours, days or weeks after death, or in milder cases they may only present after other - precipitating - illness.

Diagnosis is based on the investigations, although in some cases it is aided by positive family history and by smell; isovaleric acidaemia smells like sweaty feet, maple syrup urine disease smells of the syrup in the name, and ketosis can often be detected by the clinician.