Assessing the outcome of
fatty acid oxidation disorders is difficult, as most are rare. For diagnosis by newborn screening, the situation is compounded: far more cases are diagnosed by screening than by clinical presentation, representing a somewhat different cohort. The literature on outcome was reviewed. For disorders other than medium-chain
acyl-coenzyme A (
CoA)
dehydrogenase (
MCAD) deficiency there was insufficient evidence to make many firm statements. In
MCAD deficiency, risk of death in the first 72 h is around 4%, with a further approximately 5-7% fatality rate in the first 6 years but very low subsequent risk in previously undiagnosed patients. The risk of death after diagnosis is very low at any age, with good management. The long-term outcome is good nowadays.
Very-long-chain acyl-CoA dehydrogenase deficiency poses a risk of death in early infancy, but the condition is generally treatable, with a good outcome after diagnosis. Approximately 10-20% of patients diagnosed by newborn screening and treated nevertheless suffer episodic
rhabdomyolysis. Some patients never become symptomatic. Isolated
long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency is treatable, but most patients suffer episodic hypoketotic hypoglycaemia and
rhabdomyolysis. Generalised mitochondrial tri-functional
protein deficiency has high early mortality rate. A more insidious presentation also occurs, with symptoms sometimes confined to progressive axonal neuropathy. Among
carnitine cycle disorders,
carnitine transporter deficiency, potentially lethal, is uniformly successfully treated orally with
carnitine.
Carnitine-acylcarnitine translocase and early-onset
carnitine palmitoyl
transferase type II (
CPT II) deficiencies have an extremely high neonatal mortality rate. Late-onset
CPT II is characterised only by episodic
rhabdomyolysis on severe exercise.
CPT type IA deficiency may often be benign, although early presentation with hypoketotic hypoglycaemia certainly occurs.