Changes in the Structural Elements of the Sebaceous Hair Follicle in the Differential Diagnosis of Non-Scar Alopecia

The study investigated changes in the structural elements of the sebaceous hair follicle in 191 patients with non-scar alopecia compared to 20 control subjects. It found that the hair sac is thinner in patients with non-scar alopecia, particularly in those with alopecia areata. A decrease in the thickness of the external root sheath was observed across all alopecia types, with the most significant thinning in cases of nested and diffuse hair loss. The inner root sheath was thinner in diffuse, nesting, and seborrheic alopecia, but not in androgenic alopecia. The study concludes that in alopecia, structural thinning of the hair follicle begins at the subcutaneous fat level, unlike in non-thinning hair where changes are most significant at the transition from the reticular dermis to the sebaceous gland.