SNP Shot: Genomic Insights

Sitosterolemia is a condition characterized by the buildup of plant sterols (or phytosterols) – fatty substances from vegetable oils, nuts, and other plant-based foods – in the blood and tissues. Individuals with this disorder have significantly elevated sitosterol levels in their blood, typically 30 to 100 times higher than normal. While cholesterol, a similar fatty substance found in animal products, is often mildly to moderately elevated, particularly in affected children, some individuals with sitosterolemia have normal cholesterol levels.

The body does not produce plant sterols; they are acquired through diet. Symptoms of sitosterolemia may become apparent early in life after the introduction of plant sterol-containing foods, although some individuals remain asymptomatic.

Atherosclerosis, the accumulation of fatty deposits in the arteries, can develop in childhood in individuals with sitosterolemia. This narrowing of the arteries restricts blood flow, increasing the risk of heart attack, stroke, or sudden death.

Some individuals with sitosterolemia develop xanthomas, small yellowish growths composed of accumulated lipids, beginning in childhood. These xanthomas can appear anywhere on or just beneath the skin, commonly on the heels, knees, elbows, and buttocks. They can also occur in tendons, such as those in the hand or the Achilles tendon. Large xanthomas can lead to pain, limited movement, and cosmetic issues.

Joint stiffness and pain can also result from plant sterol deposits in individuals with sitosterolemia. Less frequently, blood abnormalities are observed, sometimes being the only indication of the disorder. Premature breakdown of red blood cells (hemolysis) can lead to hemolytic anemia, a shortage of red blood cells. Affected individuals may also have abnormally shaped red blood cells called stomatocytes and abnormally large platelets (macrothrombocytopenia).

Inheritance:

Sitosterolemia is an autosomal recessive genetic disorder. This means that an individual must inherit two copies of the mutated gene, one from each parent, to develop the condition. The parents, who each carry only one copy of the mutated gene, are typically asymptomatic carriers.