Dermatosis localized in the anogenital regionis an urgent problem of modern medicine, requiring the involvement of physicians of various specialties. Difficulties in the differential diagnosis of dermatosis in anogenital area determine the formation of severe clinical forms and torpidity to the treatment. It is important to note that in case of late diagnosis, there is a possibility of serious complications, especially in the absence of adequate treatment of dermatoses in anogenital area. The problem of differential diagnosis lies in the similar clinical picture of most skin diseases, and the effectiveness of treatment depends on the accuracy of the diagnosis. The article presents current data on epidemiology, etiopathogenesis, provoking factors, clinical features of various forms of lichen planus (LP) in anogenital area. The relationship of LP with pathological conditions such as autoimmune diseases, malignant neoplasms, viral hepatitis C, presence of dyslipidemia, hypothyroidism and diabetes in a patient is discussed. Particular attention is paid to the hypertrophic variant of LP in anogenital area, which has the most difficult clinical picture to diagnose and is the least described in the scientific literature. The authors present a complex interdisciplinary clinical case of LP in anogenital area. Dynamic monitoring, the involvement of related specialists and the use of various diagnostic methods, such as laboratory tests, dermatoscopy, histological examination, transdermal imaging methods (ultrasound, MRI), is often required. Ccombined work of a dermatovenereologist, proctologist, obstetrician-gynecologist, urologist, oncologist, pathomorphologist and the surgeon provides faster and more accurate diagnosis of diseases, which in turn allows to choose timely and adequate treatment tactics. The presented clinical case will help practitioners to better navigate the issues of diagnosing skin diseases in anogenital area.

Keywords: perianal area, anogenital area, hypertrophic form of lichen planus, vulvar lichen planus, external genitalia