The main manifestations of COVID-19 are primarily interstitial pneumonia and respiratory failure. No less than 20% of patients have variable skin rashes, which try to be interpreted as markers and predictors of the peculiarities of the course of coronavirus infection. In addition, hair loss is a characteristic manifestation of COVID-19, and the salivary follicles are regarded as a target for SARS-CoV-2. The most common variants of alopecia in patients with a new coronavirus infection or vaccine-induced alopecia are acute telogenic, nondescript, and androgenetic alopecia. This review provides information on the most common variants of hair loss in patients with SARS-CoV-2 infection, the features of their manifestations, and possible mechanisms of development. Acute telogenic hair loss is the most common variant of SARS-CoV-2-induced alopecia, is characteristic of patients with subacute course of COVID-19 and can be combined with trichodynia, anosmia and aguvia, which are markers of nervous syste damage. Given the variability in the time of onset after infection, a heterogeneous pathogenesis of alopecia can be assumed. Nested alopecia after COVID-19 is often a relapse of the disease, its severity and frequency do not correlate with the severity of the infectious disease, and its prevalence in women indicates the importance of hormonal factors in its development. Androgenetic alopecia may be a predictor of high risk of infection, severe course, and recurrence of COVID-19. The first two variants of alopecia may be associated with COVID-19 vaccination, and the latter is a predictor of inadequate immune response to vaccine administration. The mechanisms of the damaging effects of SARS-CoV-2 on hair follicles have not been fully deciphered and are most likely complex, with different leading links in different types of hair loss. Deciphering these mechanisms may provide prerequisites for understanding the mechanisms of COVID-19 damage to other tissues and organs.

Folliculitis decalvans is a rare disease of primary cicatricial alopecias, about 11% of all alopecias of this group. Dermatosis was first described by the French dermatologist Charles-Eugne Quinquaud in 1888 and 1889. In recent decades, the number of publications devoted to the etiopathogenesis, clinical and histological characteristics, as well as approaches to the treatment of folliculitis decalvans has increased. The article presents the results of data analysis on the databases Scopus, Web of Science, MedLine, The Cochrane Library, EMBASE, Global Health, CyberLeninka, RSCI. The etiopathogenesis of the disease is still unknown. The role of seborrhea and skin colonization by Staphylococcus aureus, as well as impaired local immune response and the presence of a genetic predisposition, have previously been discussed. Folliculitis decalvans is now thought to be a result of persistent disruption of the skin barrier that predisposes to subepidermal invasion by opportunistic microorganisms, including Staphylococcus aureus. Clinical, dermatoscopic (trichoscopic) and histological characteristics of dermatosis are being specified. Its characteristic clinical features are a persistent progressive course, the formation of alopecia foci with a rich red edge, pustules and crusts along the periphery of the alopecia foci, polytrichia and the formation of a dense scar that rises above the surrounding skin. Dermatoscopic characteristics depend on the intensity of the inflammatory process. Specific trichoscopic signs of the disease include follicular pustules, yellow tubular desquamation, yellow crusts, perifollicular erythema, perifollicular hemorrhages, and fine tortuous vessels. Depending on the number of these signs, the degree of inflammation is determined. Histological features of the disease include a massive perifollicular infiltrate, the formation of gaps between the epithelium of the follicles and the surrounding stroma, and in the final stages of the process ― fibrous tracts, diffuse fibrosis in the dermis. The treatment of folliculitis decalvans are antibacterial drugs, it is also possible to treat with courses of topical corticosteroids, antiseptic solutions. We assume that the systematization of information about the etiopathogenesis and approaches to the diagnosis and treatment of folliculitis decalvans will improve the diagnosis among other primary cicatricial alopecia and the choice of the tactics of treating folliculitis decalvans.