Cutaneous basophil infiltration in atopic dermatitis is associated with abundant epidermal infiltration of helper T cells: A preliminary retrospective study

Abstract Atopic dermatitis (AD) is a heterogenous inflammatory skin disorder. Our previous study revealed that basophil infiltration in skin is observed in approximately 60% of AD cases. However, the clinical and histological characteristics of AD associated with basophil infiltration remain unclear. We examined basophil infiltration by immunohistochemical staining of 38 specimens from 34 patients who underwent skin biopsies to diagnose AD from April 2016 to September 2021 at Tokyo Medical and Dental University Hospital. The patients/specimens were divided into two groups, 17 patients/21 specimens associated with little or no basophil infiltration (basophil‐low group) and 17 patients/17 specimens associated with marked basophil infiltration (basophil‐high group). The clinical characteristics of the patients (age, sex, complications, blood biomarkers, skin symptoms, and treatment) and histological features of the specimens were compared between the groups. Basophil‐high patients were significantly younger than basophil‐low patients. Blood basophil counts were higher in basophil‐high patients than in basophil‐low patients. CD4 + T‐cell infiltration was more marked in basophil‐high specimens than in basophil‐low specimens. CD4 + T cells infiltrated into the dermis as well as into the epidermis only in the basophil‐high specimens. Thus, basophil‐high AD can be characterized by skin lesions associated with abundant helper T‐cell infiltration in younger patients.