Pityriasis lichenoides: Modern ideas about pathogenesis and risk factors

Introduction. Pityriasis lichenoides (PL) is a group of relatively rare chronic skin diseases, united by some common pathogenetic links, clinical symptoms and pathohistological manifestations. The current state of the problem of PL is associated with significant difficulties not only for diagnosis and treatment, but also for determining all links of pathogenesis, and is also associated with the risk of transformation of PL into skin lymphoma, decreased quality of life and increased mortality in this group of patients. The article discusses literature data on the mechanism of development and provoking factors of PL. Aim. To analyze the literature on the features of the pathogenesis and clinical picture of PL. Materials and methods. A retrospective analysis of Russian and foreign literature sources for the period 2010–2023 was carried out, describing clinical cases of PL, features of the pathohistological picture, and modern ideas about the pathogenesis of this disease. Literature published before 2010 was not used in the analysis. Results. Many provoking factors for the development of PL have been identified, such as drugs, protein molecules of vaccines, microorganisms, etc., but their role has not been fully studied. The authors of most studies note a certain time interval between the acting trigger factor and the development of PL, as well as similar histopathological manifestations that allow to verify PL, and the clinical effectiveness of various treatment regimens. It is assumed that PL develops as a result of increased expression of certain clones of T-lymphocytes (CD8, CD30), which convert the protein structures of the epidermis into an antigenic target during antigenic cross-stimulation. Conclusion. Currently, there are no clear pathognomonic symptoms of PL, which makes it possible to classify it as a difficult-to-diagnose dermatoses and opens up broad prospects for further study of immunological and histological changes. Crossreactivity between keratinocyte proteins and protein molecules of various antigens makes it relevant to study not only groups of provoking factors, but also (perhaps to a greater extent) the immunological status of patients with PL. Alertness and appropriate diagnostic search on the part of dermatovenerologists are extremely important for timely prediction and detection of PL in a group of patients with a certain immunological predisposition.