Immune-mediated alopecias and their mechanobiological aspects

Updates on disorders in curly hair

Hair disorders, including central centrifugal cicatricial alopecia (CCCA), traction alopecia (TA), and acquired trichorrhexis nodosa (ATN), commonly occur in individuals with curly textured hair. Curly textured hair in individuals of African descent has unique properties and can present diagnostic and therapeutic challenges. CCCA has been linked to uterine leiomyoma and type 2 diabetes mellitus, as well as fibroproliferation. TA often presents with a fringe sign and can arise from high-tension hairstyles presumed to be protective. Trichoscopy is useful in establishing a diagnosis; perifollicular halos are more commonly seen than perifollicular erythema or scale in CCCA. In TA, miniaturized follicles, hair casts, and "flambeau sign" can be seen. Hairstyling practices likely contribute to TA and ATN; however, the data are mixed on the role of chemical relaxers and heat styling in CCCA. Unique considerations in the presentation of frontal fibrosing alopecia in curly textured hair have also been published recently. This review provides a comprehensive, up-to-date summary of these disorders with an emphasis on their unique properties, as well as considerations in hair care for curly textured hair.

How Our Microbiome Influences the Pathogenesis of Alopecia Areata

Alopecia areata is a multifactorial autoimmune-based disease with a complex pathogenesis. As in all autoimmune diseases, genetic predisposition is key. The collapse of the immune privilege of the hair follicle leading to scalp loss is a major pathogenic event in alopecia areata. The microbiota considered a bacterial ecosystem located in a specific area of the human body could somehow influence the pathogenesis of alopecia areata, as it occurs in other autoimmune diseases. Moreover, the Next Generation Sequencing of the 16S rRNA bacterial gene and the metagenomic methodology have provided an excellent characterization of the microbiota. The aim of this narrative review is to examine the published literature on the cutaneous and intestinal microbiota in alopecia areata to be able to establish a pathogenic link. In this review, we summarize the influence of the microbiota on the development of alopecia areata. We first introduce the general pathogenic mechanisms that cause alopecia areata to understand the influence that the microbiota may exert and then we summarize the studies that have been carried out on what type of gut and skin microbiota is found in patients with this disease.