A rare inherited disorder characterized by congenital
hypercholesterolemia, presenting clinically with tendon xanthomas, premature
coronary artery disease, and premature atherosclerosis.
First described in 1974 by Battacharyya and Connor in two sisters.
As of year 2000, in the United States approximately 50
patients have been identified. The incidence is suggested at 1:1,000,000 population. No ethnic predilection.
Autosomal recessive. The gene defect in
sitosterolemia remains to be elucidated.
The nature of the primary defect is unknown at the
molecular level, although enhanced intestinal absorption and reduced
excretion of plant sterols appear to be the abnormality. Affected homozygote
individuals show an enhanced absorption of both cholesterol and sitosterol
from the diet, and decreased bile clearance of these sterols and their
metabolites, resulting in markedly expanded whole-body cholesterol and
sitosterol pools. Increased content of sitosterol in red cells may be
responsible for the fragility of the RBCs and results in chronic hemolytic
Sitosterolemic homozygotes show elevation of plasma
plant sterol (sitosterol and campesterol) concentrations.
Absorption of sitosterol in affected patients is
20 to 30%, as compared to 5% in normal individuals. The plasma
concentrations of sitosterol in affected patients varies between 15 and
27% of the total sterol content and increased concentrations are found in
cell membranes, xanthomas, and atherosclerotic plaques. Tendon and tuberous
xanthomas developed at an early age, as with early development of
atherosclerosis, and episodes of hemolysis and painful arthritis are
features. Coronary atherosclerosis is common. Phytosterols can cause
cholestasis in susceptible infants. Extramedullary sitosterolemic xanthomas
have been reported to result in spinal cord compression. Episodic hemolysis
and chronic hemolytic anemia may be present.
Detailed cardiovascular assessment.
Where indicated, not only should the global ventricular function be assessed by
echocardiography, but angiography with angioplasty may improve coronary flow
prior to elective surgery. Elective surgery should be postponed until at
least 6 months from any myocardial infarction. Current congestive heart
failure also carries higher risk of another perioperative cardiac event.
Obtain drug history (nitrates, beta blockers, calcium channel blockers,
antiplatelet agents, digoxin). Patients with painful arthritis may be on
long-term nonsteroidal anti-inflammatory drugs (NSAIDs). The signs and symptoms of anemia must be sought. Anemia is
poorly tolerated in patients with coronary artery disease and every effort
should be made to correct the deficit preoperatively. Investigations: cell blood count, ECG, chest
radiograph, coagulation studies, and bleeding time if the patient is on
antiplatelet agents and/or heparin. Premedication with adequate sedation to
reduce anxiety, continue medical therapy, and administer oxygen therapy
during transport to the operating theatre.
The conduct of anesthesia and the choice
of monitors depend primarily on the underlying cardiac status of the
patient, and the type and extent of the proposed surgery. Aim to maintain
optimal myocardial oxygen supply-demand balance (avoid hypoxemia,
sympathetic stimulation, pain, and tachycardia). A central neuraxial block
(spinal, epidural) is relatively contraindicated in those patients ...