Nemolizumab for Lichen Amyloidosis With Serial Serum Interleukin‐31 Levels: A Case Report

Lichen amyloidosis (LA) is a chronic, intensely itchy skin disease that is often difficult to control with conventional therapies. Interleukin-31 (IL-31) is an itch-driving cytokine, and nemolizumab, an antibody to the IL-31 receptor, has become available for some pruritic dermatoses. We report a man in his 60s with a 6-year history of treatment-refractory LA on the trunk and extremities. He received nemolizumab 60 mg subcutaneously every 4 weeks because of persistent severe itch despite topical therapy. Itch intensity improved from 5/10 at baseline to 2/10 at Week 4 and to 1/10 at Week 8, remaining low thereafter. The papular lesions showed marked flattening and regression after five doses, leaving only faint residual pigmentation. Serum IL-31 concentrations were measured immediately before each injection using a commercial assay. Values decreased after Week 4, reached the lowest level by Week 12 during near-complete remission, and showed a mild increase by Week 16 without clinical relapse. This case suggests that blocking IL-31 signaling can rapidly and durably improve severe LA and that repeated serum IL-31 measurements may help support treatment response over time.