Histopathological investigation of clinically non-affected perilesional scalp in alopecias detected unexpected spread of disease activities

Histopathological comparison between clinically affected and intact regions in alopecia patients has been considered to facilitate better understanding of the pathophysiology of ongoing disease. Theoretically, adjacent intact regions should provide ideal controls as they should share close histological characteristics, however, to what extent clinically non-affected neighboring regions maintain their pathological integrity has not been fully assessed. The goal of this study is to delineate histopathological characteristics of clinically intact perilesional regions in the patients with various forms of alopecia. Transverse sections of 4-mm punch biopsy at the levels of isthmus and suprabulbar portion were obtained from seemingly unimpaired perilesional scalp of 50 Japanese alopecia patients (16 alopecia areata [AA] multiplex, 19 scarring alopecia [SA], 15 other conditions) and subject to histopathological investigation. Initial screening detected decrease in anagen (anagen: telogen ratio = 82.4:17.6) when compared with previously reported standard hair counts in normal Asian scalp. This finding prompted further investigation. Unexpectedly, 33 (66%) specimens demonstrated some microscopic abnormalities, 10 (62.5%) AA specimens showed increase in telogen ratio, vellus hair count and miniaturization, while perifollicular inflammatory cell infiltration was detected in 5 (26.3%) SA cases. Exclusion of histologically affected specimens yielded average hair count numbers resembling those reported in Koreans, supporting the pathological integrity of selected samples and, more importantly, indicating normal hair counts in east Asians. These findings indicated a less recognized significance of histopathological investigation of clinically non-affected perilesional scalp in alopecias for better assessment of the spread of disease activities, which should enable better management of hair loss conditions.