Primary cicatricial alopecia: Recent advances in understanding and management

Primary cicatricial alopecias (PCA) are a rare group of disorders, in which the hair follicle is the main target of destructive inflammation resulting in irreversible hair loss with scarring of affected lesions. The most typical clinical manifestation of PCA is the loss of visible follicular ostia. The histopathological hallmark of a fully developed lesion is the replacement of the hair follicle structure by fibrous tissue. PCA could share similar clinical manifestations and eventually lead to "burn-out" alopecia. Some subsets are hardly distinguishable histopathologically and the mechanisms that elicit such a destructive reaction have not been fully elucidated. Thus, the management of PCA represents one of the most challenging clinical problems for dermatologists. The aim of this review is to provide a concise and comprehensive summary of recent advances in PCA management, especially focusing on novel methodologies to aid diagnosis, and updates on our understanding of the etiopathogenesis. Dermoscopy, a new pathological preparation technique and direct immunofluorescence analysis enable more accurate clinicopathological diagnosis of PCA. Microarray analysis may be beneficial to distinguish PCA subtypes. Currently suggested mechanisms underlying PCA include loss of immune protection of stem cells, impaired stem cell self-maintenance, enhanced autoimmunity by pro-inflammatory cytokines and environmental/genetic predispositions. Interestingly, recent data indicates the association between lipid metabolism dysregulation and PCA development, implying an important role of the sebaceous gland dysfunction in the etiopathogenesis. Based on that hypothesis and observations, novel therapeutic approaches have been proposed, including the use of peroxisome proliferator-activated receptor-γ agonist for lichen planopilaris.