Atopic Dermatitis-Like Rash During Evolocumab Treatment of Familial Hypercholesterolemia

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a serine protease that targets the low-density lipoprotein (LDL) receptor for lysosomal degradation. PCSK9 impedes the receptor-mediated clearance of LDL-cholesterol, thereby increasing serum LDL-cholesterol levels. Evolocumab, a human monoclonal antibody against PCSK9, effectively reduces serum LDL-cholesterol levels. We report the first known case of a patient who developed an atopic dermatitis (AD)-like rash during evolocumab therapy. A 43-year-old Japanese man with heterozygous familial hypercholesterolemia was treated with subcutaneous injection of 140 mg evolocumab biweekly, for 16 months. The therapy was then changed to subcutaneous injection of 420 mg evolocumab monthly. A few days after the first dose, the patient experienced pruritus and rash on his extremities. The rash worsened, while the pruritus subsided, then relapsed after the second and third doses. He had erythema and excoriation on his legs, lichenification over his popliteal fossa, xerosis on his forearms, an increased serum IgE level, and a family history of AD in his siblings. We made a provisional diagnosis of AD characterized by enhanced type 2 helper T (Th2) activity and treated him with topical corticosteroids and oral anti-histamines. His rash improved and did not relapse after the fifth dose; however, his LDL-cholesterol level increased. PCSK9 or oxidized LDL activates macrophages or dendritic cells, respectively, and enhances their activity to induce Th1 cells antagonizing Th2 cells. We hypothesized that high-dose evolocumab may suppress Th1 activity to antagonize Th2, and unmask Th2 disposition based on the patient's atopic diathesis, triggering the rash mimicking AD. Clinicians should be aware of rash development during evolocumab therapy.