Sequential cyclic changes of hair roots revealed by dermoscopy demonstrate a progressive mechanism of diffuse alopecia areata over time

Abstract

Background Diffuse alopecia areata (DAA) often leads to a complete hair shedding within a few months. Objective To explore features and mechanisms underlying DAA. Materials and Methods Scalp and hair root dermoscopy were conducted on 23 DAA patients throughout the disease process, 20 patchy Alopecia areata patients, 23 acute telogen effluvium (ATE) patients and 10 normal controls. Histopathology was also evaluated. Results We found almost all hair roots were anagen in early stage DAA in 18 patients (18/23, 78.3%) within the first 4‐8 weeks after hair loss onset. Anagen effluvium (~4 weeks) was followed by catagen (~4 weeks) and then telogen/exogen (~8 weeks) effluvium with overlap. Hair root and proximal hair shaft depigmentation was more prominent in later DAA disease stages. Black dots, exclamation mark hairs and inconsistent thickness of hair shafts were found more often in early than later DAA (Ps < 0.01). Early DAA histopathology revealed more prominent inflammation and hair follicle regression than that observed in the later stages. Patchy alopecia areata patients showed mixed anagen, catagen and telogen hair roots while ATE patients showed increased exogen and mildly decreased hair root pigmentation. Conclusion Sequential cyclic staging of shed hairs in DAA indicates the insult may be hair‐cycle specific. We suggest that DAA is initially an anagen effluvium disease involving an intense inflammatory insult, later progressing to a brief catagen effluvium, and then to telogen effluvium with premature exogen, in later stages of DAA.

Hair follicle immune privilege and its collapse in alopecia areata

“…Through its long history, a link between AA and inflammation has been well recognized 262 . It presents with a wide array of clinical and aetiological variations, 263,264 but in all instances it is a non‐scarring alopecia 265,266 . Histopathological examination reveals anagen stage HFs affected by a peri‐ and intra‐follicular inflammatory cell infiltrates primarily comprised of CD8 + T cells and CD4 + T cells, 267 as well as antigen‐presenting cells (APCs), 259,268 mast cells, 179 NK cells 88 and sometimes eosinophils 269 .…”

New developments in hair research

“…Diffuse AA was only identified as a distinct diagnosis in 1945, but it has perplexed many over the years since. Zhang et al, present a detailed investigation into the progression of diffuse AA by examination of hair roots . They confirm that diffuse AA is initially an anagen effluvium, only later progressing to a telogen effluvium pattern of hair loss.…”

The Evolving Pathogenesis of Alopecia Areata: Major Open Questions

“…All currently available evidence suggests that the characteristic AA hair loss phenotype simply does not occur without this peculiar constellation (Gilhar et al, 2012;Paus et al, 2018). Notably, however, with increasing chronicity, the character of the AA phenotype dynamically changes from an anagen effluvium in acute, rapidly progressing AA into a telogen effluvium with premature exogen in the chronic stage (Zhang et al, 2020). We also know that CD8þ T cells alone suffice to elicit AA-like hair loss lesions, whereas autoantibodies directed against HF antigens fail to do so (de Jong et al, 2018;Gilhar et al, 2012Gilhar et al, ,1998.…”