Homozygous phytosterolemia and a literature review: A case report.

Background: Phytosterolemia, also known as sitosterolemia, is a rare autosomal recessive disease characterized by elevated plasma plant sterol levels and xanthomata, which is easily misdiagnosed as familial hypercholesterolemia. Patients with homozygous phytosterolemia often have severe clinical manifestations, with xanthomata in childhood and premature atherosclerosis. Our patient had a milder clinical phenotype.

Case summary: This report describes a patient with homozygous phytosterolemia who presented with only elevated cholesterol and low-density lipoprotein cholesterol (LDL-C) without xanthomata, arteriosclerosis, or hematological abnormalities. Homozygous mutation of ABCG5 which encodes an ATP-binding cassette transporter, was detected by whole exome sequencing and diagnosed as phytosterolemia. Measurement of the patient's plasma plant sterol levels detected significant elevations in stigmasterol, rapeseed oil-derived plant sterol, and β-glutaminol levels. Ezetimibe was started and a low plant sterol diet was recommended. The patient's blood lipid profile was reexamined one month later and showed significant decreases in total cholesterol and LDL-C levels. Phytosterolemia has similar clinical features as familial hypercholesterolemia, is highly susceptible to misdiagnosis, and has a very low incidence, and therefore clinicians need to consider a genetic diagnosis of a definitively hyperlipidemic disorder when statin drugs fail to lower lipid levels.

Conclusion: Phytosterolemia is easily misdiagnosed as familial hypercholesterolaemia and can be treated by dietary modification and cholesterol absorption inhibitors to lower blood lipids.