[What's new in dermatological research?].

Medical literature is rich with new and relevant information, resulting from basic or applied research. Some strong arguments are presented in this document. Firstly, the discovery and role of a virus, the polyomavirus, in the development of Merkel tumours. It is a small virus with double bit DNA strand, coding for a oncoprotein. If the polyomavirus plays a causal role in the tumorigenesis, it acts by various mechanisms. The micro-RNAs represent an abundant class of small RNA not coding for proteins, but which control the gene expression coding for proteins on a post-transcriptional level. The first obvious sign of the role of the micro-RNAs in the inflammatory dermatoses appeared recently, in particular when these micro-RNAs associated with psoriasis and atopic dermatitis were identified through a broad genomic analysis of the expression of these micro-RNAs. A new giant virus strain sheltering another unknown tiny virus to date has just been discovered. This virus infinitely small called Sputnik enables to deteriorate a much larger virus baptized Mama, at the point of preventing it to manufacture normal viral particles and also preventing it from reproducing. This discovery raises a crucial question: Is Sputnik a new system of transfer of genes of a species of one virus to another? A group of blood cells expressing E-cadherin, the dot cells, found in the fetal blood of the dermis, contributes to tissue repair through the mechanisms of cellular differentiation and their action allows healing without scar. CD4+ T helper lymphocytes producing interleukin 17 (IL17) play a pathogenic part in atopic dermatitis. The genes of the beta defensins could be involved in the genetic susceptibility of the psoriatic disease. The autoimmune origin of the alopecia areata is supported by a great number of observations, the role of neuropeptides in the initiation of the autoimmunity during alopecia areata has just been demonstrated. The dendritic cells are cells presenting antigens which play a crucial role in the adaptive immunological response. It was shown that activation of the proliferation of the lymphocytes T after the migration of dendritic cells on the level of the lymphatic ganglion depended not on Langerhans cell, but of the dendritic cell. A new way appears to control the autoimmunity in the psoriasis and involves the plasmacytoid dendritic cells which are sensitized with the DNA itself when it is coupled with an antibacterial peptide. Mast cells express cathelicidin, which acts like an antibiotic with broad spectrum and influences the defence system of the epitheliums. We have perhaps found a new therapeutic target for rosacea by disclosing high rates of cathelicidin and a series of associated proteases in skin lesions. The sebocytes express antibacterial functional peptides deriving from cathelicidin which can have a bactericidal effect against P. Acnes. A vast genomic study in the androgenetic alopecia highlighted the existence of new loci localized on the 20p11 chromosome, associated with the risk of androgenetic alopecia. New alleles to determine the color of hair and the cutaneous pigmentation were identified. Two loci (IRF 4 and SLC24A4) are highly associated with the color of hair, like three other areas. The blue color of the eyes could be due to a change of an element located in gene HERC2 preventing of the expression of OCA2. Thus, many fields of dermatology were the object of research which opens new prospects for diagnosis and treatment.