Distinctive age distribution and hair loss pattern putatively highlighting uniqueness of Japanese cases of fibrosing alopecia in a pattern distribution

Recent Advances in Understanding of the Etiopathogenesis, Diagnosis, and Management of Hair Loss Diseases

Hair-loss diseases comprise heterogenous conditions with respective pathophysiology and clinicopathological characteristics. Major breakthroughs in hair follicle biology and immunology have led to the elucidation of etiopathogenesis of non-scarring alopecia (e.g., alopecia areata, AA) and cicatricial alopecia (e.g., lichen planopilaris, LPP). High-throughput genetic analyses revealed molecular mechanism underlying the disease susceptibility of hair loss conditions, such as androgenetic alopecia (AGA) and female pattern hair loss (FPHL). Hair loss attracted public interest during the COVID-19 pandemic. The knowledge of hair loss diseases is robustly expanding and thus requires timely updates. In this review, the diagnostic and measurement methodologies applied to hair loss diseases are updated. Of note, novel criteria and classification/scoring systems published in the last decade are reviewed, highlighting their advantages over conventional ones. Emerging diagnostic techniques are itemized with clinical pearls enabling efficient utilization. Recent advances in understanding the etiopathogenesis and management for representative hair diseases, namely AGA, FPHL, AA, and major primary cicatricial alopecia, including LPP, are comprehensively summarized, focusing on causative factors, genetic predisposition, new disease entity, and novel therapeutic options. Lastly, the association between COVID-19 and hair loss is discussed to delineate telogen effluvium as the predominating pathomechanism accounting for this sequela.

Primary cicatricial alopecia: Recent advances in evaluation and diagnosis based on trichoscopic and histopathological observation, including overlapping and specific features

Primary cicatricial alopecia (PCA) is a form of alopecia in which inflammatory cells target follicles, including the bulge region containing follicular stem cells, leading to permanent alopecia. New classifications of PCA subtypes have recently been proposed, including those that account for novel trichoscopic and histopathological features of PCA, enabling greater precision in the evaluation and diagnosis of this condition. Nonetheless, diagnosis remains challenging clinically and histopathologically because the etiology of PCA is multifactorial. Inconsistent use of terminology, overlapping disease concepts, and changes in the clinical or histopathological severity of inflammation in the disease course in the same patient also make diagnosis quite challenging. The present study comprehensively reviews recent progress in diagnostic techniques, including the use of clinical, trichoscopic, and histopathological features, in evaluating each PCA subtype, containing overlapping and specific features. Elucidating the features of PCA, including those that are common to multiple subtypes as well as specific to each in both early and advanced-stage lesions, is important for accurate diagnosis. Improving the evaluation and treatment of this disease depends on having a broader clinical understanding that takes into account not only the features of the disease at a given point in time, but also the changes that occur during the entire disease course.