Carnitine palmitoyltransferase (CPT) deficiency is a
group of disorders caused by defects in the enzymes CPT I or II. Type I is
the most common human lipid myopathy. The metabolic myopathy can be
triggered by effort, anesthesia/surgery, or stress and results in episodes
of rhabdomyolysis and myoglobinuria.
Metabolic Myopathy and Carnitine Palmitoyltransferase
CPT deficiency is the most common metabolic cause of
Autosomal recessive. Three polymorphisms and
more than 20 mutations have been identified in the CPT2 gene among patients with
CPT II deficiency, with the responsible genetic defect mapped to 1p32. The
mutations for the hepatic and muscle isoforms of CPT I are located on 11q13
and 22q13.3, respectively.
CPT I and II exist as two functionally distinct
mitochondrial enzymes, embedded in the outer (CPT I) and inner (CPT II)
mitochondrial membranes. Both are involved in facilitation of the
transmembranous transport of fatty acids into the mitochondria.
Skin/muscle biopsy may be required to confirm the
diagnosis. Prompt diagnosis can help to avoid risk factors and to prevent
rhabdomyolysis and renal failure secondary to myoglobinuria.
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
Liver and renal function and serum
levels of electrolytes, carnitine, glucose, creatine kinase, and ammonia
should be assessed preoperatively. Twelve-lead and/or
Holter electrocardiography may be required if the history or examination
suggests arrhythmias. In case of cardiomyopathy, echocardiography is
recommended. The preoperative fasting period should be kept as short as
possible. The recommendation is to start a dextrose-containing infusion at
the beginning of the fasting period. Sedative and anxiolytic premedication
may be helpful in reducing perioperative stress.
Acute deteriorations including coma and
rhabdomyolysis may be precipitated by fasting, hypoglycemia, and
perioperative stress. The minimum allowable duration of fasting should be
considered, and patients should ...