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Viral infections are increasingly a global health problem, but not only because of the current COVID pandemic and acute diseases, but also because of the long-term consequences. The authors shortly describe the main characteristics of hepatitis B and C and tropical viral diseases (dengue, Zika, chikungunya), focusing on dermatological symptoms and also provide a brief current literature review, as well as national aspects related to each pathogen.

Primary cutaneous lymphomas are tumors that appear primarily in the skin. The subtypes of the second most common form of extranodal non-Hodgkin’s lymphoma have different clinical, histological, immunological, and molecular characteristics. The most common type of them is mycosis fungoides (MF) and rare its leukemic variant Sézary syndrome (SS). Both diseases are type Th (CD4 +T helper) cells of origin. The development of immunology and molecular biology techniques have significantly expanded our knowledge of pathogenesis. Today, it is proven that MF and SS are derived from different groups of T cells: SS from central memory T cells and MF from skin-resident effector memory T cells. Th2 differentiation characteristic of tumor cells can also be promoted by the microenvironment of the tumor. The non-malignant cellular infiltrate has a role in the pathomechanism: either in tumor initiation, progression, or in the selection and promotion of malignant cells, as well as in the development of the general immunosuppressive state characteristic of advanced stages. The paper discusses new knowledge on the pathogenesis of MF and SS, demonstrating new therapeutic options.

Ultraviolet (UV) light is absorbed by nucleic acids, proteins or other endogenous chromophores, such as porphyrins, flavins and melanin, triggering biological processes in skin cells. Both UV-induced mutations in melanocytes and changes in the immune microenvironment are understood to play a role in the development of cutaneous melanoma. The degree of UV-induced stress and the protection against this stress are influenced by both intracellular and intercellular molecular interactions. The present review summarizes the known major molecular biological changes induced by UV light in the skin that play a role in melanoma initiation and promotion. Nevertheless, cutaneous melanoma is not a homogenous disease, and the interaction of variable environmental exposure and different genetic susceptibility and other host factors lead to the formation of melanomas with different biological behavior and clinical characteristics. This review highlights the challenges in the understanding of how UV radiation contributes to the formation of cutaneous melanoma, and reviews the new results of photobiology and their link to tumor genetics and tumor immunology with potential implications on melanoma prevention and therapeutic strategies. The information presented here is expected to add clarity to ongoing research efforts in this field to aid the development of novel strategies to prevent and treat melanoma.