Central centrifugal cicatricial alopecia severity is associated with cowhage-induced itch

Abstract

Patients with central centrifugal cicatricial alopecia (CCCA) often suffer from varying degrees of itch, pain and burning sensations. However, the neural component of these skin sensations has not been assessed. To conduct a comprehensive analysis of C nerve fibre function relating to itch and pain perception in patients with CCCA using thermosensory testing and experimental itch models. Fifteen healthy African-American women and 16 African-American female patients with CCCA participated in the study and underwent quantitative computerized thermosensory testing to assess warmth and heat pain thresholds. Itch was induced using histamine iontophoresis and application of cowhage spicules, and the intensity of each itch was assessed. The association between itch intensity and CCCA severity score was examined. A positive correlation between CCCA severity score and peak itch ratings of cowhage on the lesional scalp (crown) was observed (P = 0·023, r = 0·562). Notably, the histamine peak itch rating was not found to have a significant correlation with CCCA severity score (P = 0·913). The crown also had significantly higher warmth and pain thresholds than the occiput in both healthy subjects and patients with CCCA. Our results suggest a putative role for the protease-activated receptor (PAR)-2, which is activated by cowhage, in the pathogenesis of CCCA. Future studies should examine PAR-2-directed therapeutics for patients with CCCA. Examining for itch and other dysaesthesias in patients with CCCA is of vital importance to dermatologists in assessing disease severity.