Abstract.Sitosterolemia is a rare, autosomal recessively inherited disorder of lipid metabolism
caused by mutations in the “ATP-binding cassette, subfamily G” member 5 and 8 proteins
(encoded by the ABCG5 and ABCG8 genes, respectively),
which play critical roles in the intestinal and biliary excretion of plant sterols. We
report the clinical features and treatment outcomes of an 18-month-old Japanese girl with
sitosterolemia, who presented with multiple linear and intertriginous xanthomas around the
joint areas. Serum lipid analyses revealed elevated levels of total cholesterol (T-Chol:
866 mg/dL), low density lipoprotein-cholesterol (LDL-C: 679 mg/dL), and plant sterols
(sitosterol: 24.6 mg/dL, campesterol: 19.2 mg/dL, stigmasterol: 1.8 mg/dL). Compound
heterozygous mutations (p.R419H and p.R389H) were identified in ABCG5.
The patient was placed on a low cholesterol/low plant sterol diet and treated with
colestimide (a bile acid sequestrant) and ezetimibe (an NPC1L1 inhibitor). Serum T-Chol
and LDL-C levels decreased to normal within 2 mo, and plant sterol levels decreased by 30%
within 4 mo. The xanthomas regressed gradually, and almost completely disappeared after
1.5 yr of treatment. No further reductions of plant sterol levels were observed. Long-term
follow-up is important to verify appropriate therapeutic goals to prevent premature
atherosclerosis and coronary artery disease.