Guarrera Marcella, Rebora Alfredo
Dermatologic Clinic, University of Genoa, Genoa, Italy.
Skin Appendage Disord. 2017 Oct;3(4):193-196. doi: 10.1159/000460300. Epub 2017 May 12.
Contrary to the classical view of the hair cycle, in which telogen is the resting phase that precedes the release of the hair shaft, another phase has been introduced, exogen. Exogen is the phase wherein the processes for the release of the hair shaft are initiated and successfully executed. Exogen ends when the shaft is liberated. Accordingly, human hairs would be preferably released not with telogen but with exogen roots. To better understand this somehow revolutionary point and what occurs in telogen effluvium (TE) and in androgenetic alopecia (AGA), we undertook a morphological study. We examined 25 women of comparable age by collecting shedding hairs by the Modified Wash Test under stringent diagnostic criteria. Eight patients were "normal", 5 had AGA, 9 TE, and 3 had a TE+AGA overlap. Hair roots were divided into early telogen, full telogen, and exogen. Exogens accounted, in normal women, for 2.6% of all hairs, for 5.2% in AGA, for 6.6% in TE, and for 2.3% in TE+AGA, without any significant difference. Our exogen prevalence (2.6%) did not vary in patients with AGA and TE. Therefore, the pathogenetic role of exogen in AGA and TE seems negligible.
与毛发周期的经典观点相反，在经典观点中休止期是毛干脱落之前的静止阶段，现在引入了另一个阶段，即脱落期。脱落期是毛干开始并成功完成脱落过程的阶段。当毛干脱落时，脱落期结束。因此，人类毛发最好是带着脱落期的发根而非休止期的发根脱落。为了更好地理解这个在某种程度上具有革命性的观点以及休止期脱发（TE）和雄激素性脱发（AGA）中发生的情况，我们进行了一项形态学研究。我们通过改良水洗试验在严格的诊断标准下收集脱落的毛发，对25名年龄相仿的女性进行了检查。8名患者“正常”，5名患有AGA，9名患有TE，3名患有TE + AGA重叠症。毛根分为早期休止期、完全休止期和脱落期。在正常女性中，脱落期毛发占所有毛发的2.6%，在AGA中占5.2%，在TE中占6.6%，在TE + AGA中占2.3%，无显著差异。我们的脱落期毛发发生率（2.6%）在AGA和TE患者中没有变化。因此，脱落期在AGA和TE中的致病作用似乎可以忽略不计。
