CPT I exists in hepatic and muscle isoforms. To
date, only hepatic CPT deficiency has been reported to cause clinical
symptoms. In infancy, hepatic CPT I normally presents as recurrent
hypoketotic, hypoglycemic coma triggered by fasting, exercise, intercurrent
illness, cold stress, or a high-fat/low-carbohydrate diet. Additional
findings during these acute episodes include metabolic acidosis,
hepatomegaly with raised transaminases, hyperammonemia, and seizures. CPT I
is normally not associated with cardiomyopathy or myopathy, although
arrhythmias have been reported in pediatric patients, particularly in the
infantile form. The results of liver function tests may remain pathologic
for a few weeks before normalization is reestablished. CPT II deficiency is
most commonly manifested in adulthood as intermittent episodes of
myoglobinuria and myalgia occurring after exercise, fasting, sleep
deprivation, (febrile) intercurrent illnesses, and anesthesia/surgery.
Acute renal failure and cardiac arrest secondary to anesthesia-related
rhabdomyolysis have been described. Between attacks, the patients may be
asymptomatic, and electromyography, serum creatine kinase activity, and the
response of serum lactate to ischemic exercise usually are normal. A rare
infantile form of CPT II deficiency may present as fatal hypoglycemia with
coma and/or with multiorgan involvement (cardiomyopathy, hepatic failure, and
muscle weakness).