Early tendon xanthomas in a breastfed toddler with sitosterolemia misdiagnosed as familial hypercholesterolemia: Successful treatment with ezetimibe

Sitosterolemia is a rare autosomal recessive disorder of sterol metabolism, often misdiagnosed as familial hypercholesterolemia due to overlapping features of tendon xanthomas and severe hypercholesterolemia. We report a 1.5-year-old breastfed female who presented with multiple tendon xanthomas, marked low-density lipoprotein-cholesterol elevation, and poor response to statins, dietary measures, and cholestyramine. Genetic analysis confirmed a compound heterozygous mutation in ABCG8 . Following initiation of ezetimibe, her lipid profile normalized, and xanthomas stabilized without adverse effects. This case underscores the need to consider sitosterolemia in early-onset xanthomas while highlighting the exacerbating effect of breastfeeding and supporting the safe use of ezetimibe in young children.