Disorders of Hair Growth and the Pilosebaceous Unit: Facts and Controversies

The document from 2013 reviews the controversies surrounding hair growth disorders, specifically alopecia areata incognita (AAI), pseudopelade of Brocq (PPB), and the link between psoriasis and alopecia. It notes the lack of consensus on diagnostic criteria for AAI and PPB, as well as the unclear epidemiology of PPB. The document also discusses psoriatic alopecia, which can manifest in various patterns and may not be directly caused by psoriasis, although hair loss can occur in psoriatic lesions, often with regrowth after treatment. Additionally, it mentions a study by Doyle et al. that found anti-TNF-α agents, used for treating chronic inflammatory diseases, can induce psoriatic lesions and alopecia, suggesting this should be considered a separate diagnostic entity. The study observed psoriasiform and alopecia areata-like changes in scalp biopsies, with features that distinguish it from primary psoriatic alopecia. The document emphasizes the need for further research to better understand these disorders and improve diagnostic criteria.