Granuloma annulare: modern concepts of pathogenesis and pathogenetically based therapy (literature review)

Granuloma annulare is a chronic, benign, non-infectious skin disorder that causes ring-shaped papules, most commonly on the hands and feet. The condition is considered rare, according to some data, it affects less than 0.04% of the population. However, in recent years there has been an increase in the incidence of dermatosis, which is associated with the high prevalence of infectious diseases, including infections caused by the SARS-CoV-2 coronavirus. The pathogenesis of granuloma annulare has not been fully deciphered; nevertheless, comparative analysis of a wide range of biomarkers in biopsies of affected skin has shown differences in the expression of genes involved in regulation of innate immunity, Th1 and Th2 lymphocytes, and Janus kinases. Associations of granuloma annulare with endocrine, immune, and autoimmune diseases, malignant neoplasms, as well as the triggering role of infections and vaccinations, are subjects of discussion, despite advances in understanding the molecular mechanisms of disease development. The treatment of granuloma annulare presents quite complex challenge. Topical corticosteroids can be effective in localized forms of the disease. Calcineurin inhibitors can be used in combination with them. For disseminated forms of the dermatosis, narrowband medium wave ultraviolet therapy at 311 nm, PUVA, and 308 nm excimer ultraviolet light therapy are prescribed. There are descriptions of the effectiveness of antibacterial drugs. Currently, TNF-α inhibitors, JAK inhibitors and IL-23 inhibitors are proposed as targeted therapy for granuloma annulare. The basis for this recommendation is the latest information about the pathogenesis of granuloma annulare. The presented literature review systematizes modern concepts of molecular and cellular mechanisms of granuloma annulare development, infectious and non-infectious triggers of inflammation, the role of endocrine, immune and oncological pathology as predisposing factors. Significant importance is given to the analysis of treatment methods of the disease.