Objective: To describe a patient with tuberous xanthomas and high levels of cholesterol and triglycerides, who was found to have type III hyperlipoproteinemia (HLP) and a rare apolipoprotein E (apoE) mutation.
Methods: We present a case report with extensive clinical, laboratory, and genetic documentation.
Results: A 33-year-old African American man presented for evaluation of hypertriglyceridemia. His medical history was remarkable for schizophrenia necessitating ongoing olanzapine therapy for the past 6 years. A few months after olanzapine treatment was begun, he noted the development of nontender, firm, papular skin lesions on his elbows and knees. His family history was negative for lipid disorders or premature vascular disease. Physical examination revealed the presence of prominent tuberous xanthomas on both elbows and knees. Results of a lipid panel demonstrated a total cholesterol level of 374 mg/dL (9.7 mmol/L) and triglycerides of 828 mg/dL (9.3 mmol/L). A work-up for causes of secondary hyper-triglyceridemia was negative. Results of apoE genotyping by a commercial laboratory showed the E3/E3 genotype, based on gene sequencing at codons 112 and 158. Because the skin lesions were typical for type III HLP, his entire apoE gene was sequenced. This analysis revealed an apoE2/E2 (arginine 145 to cysteine) mutation, previously reported to be a rare cause of type III HLP in 5 patients of African descent. Triglyceride-lowering therapy with gem-fibrozil was initiated, in addition to lifestyle modification. At follow-up several months later, total cholesterol was 276 mg/dL (7.14 mmol/L) and triglycerides were 479 mg/dL (5.41 mmol/L).
Conclusion: We speculate that olanzapine therapy, with its known metabolic side effects, exacerbated this patient's underlying lipoprotein metabolic abnormality. To our knowledge, this is the first report of an association between olanzapine therapy and tuberous xanthomas and the sixth report of this rare apoE2/E2 (arginine 145 to cysteine) mutation in the literature.