Severe Atopic Dermatitis With Increasing Daytime Sleepiness Following Nemolizumab Administration: A Case Report.

Atopic dermatitis (AD) often impairs daytime activities and quality of life (QOL) owing to intense pruritus, which disrupts sleep. Nemolizumab, an interleukin (IL)-31 receptor α inhibitor, has emerged as a promising treatment that can alleviate itching and enhance both nighttime rest and daytime functioning. We report the case of a 16-year-old boy with severe AD that was refractory to multiple therapies, including topical steroids, immunomodulators, topical Janus kinase (JAK) and phosphodiesterase 4 (PDE4) inhibitors, moisturizers, and oral antihistamines. Subcutaneous administration of nemolizumab was initiated, resulting in significant improvements in the Eczema Area and Severity Index (EASI), Patient-Oriented Eczema Measure (POEM), and Atopic Dermatitis Control Tool (ADCT) scores. However, he exhibited a marked increase in the Epworth Sleepiness Scale (ESS) the day after each injection, accompanied by pronounced daytime drowsiness lasting one to two weeks. Upon discontinuation of nemolizumab at the patient's request, daytime sleepiness resolved. Although nemolizumab is expected to reduce pruritus and improve daytime alertness, our patient exhibited paradoxical post-injection hypersomnolence. Possible contributors include shifts in the circadian rhythm or central nervous system effects related to IL-31 inhibition, although the precise mechanism is yet to be established. Therefore, careful monitoring of both dermatologic outcomes and daytime vigilance is essential. Clinicians should be aware of potential post-injection sleepiness when administering nemolizumab, given that it is an otherwise effective treatment for severe AD.