EMC - Dermatologie-Cosmétologie最新文献

Seborrheic dermatitis is a common facial dermatitis that affects 1 to 3 % of the adult population. The incidence of the disease is higher in some diseases such as HIV infection, Parkinson's disease or mood disorders. This dermatitis presents as red, flaking patches of skin located where seborrhoea activity is maximal. Two mechanisms are important to understanding seborrheic dermatitis: Malassezia yeasts and seborrhoea. Most of the time, topical treatment is successful. Controlled trials have demonstrated the efficacy of ketoconazole, ciclopirox olamine and lithium gluconate.

Lichen planus is a chronic itching dermatosis of the adult, characterized by shiny flat violaceous polygonal papules. It may affect any part of the body surface, but it is most likely to appear on the extension part of the limbs. Mucous-membrane lesions are very common. Atypical forms are usual. Histological features are a superficial band-like infiltrate of lymphocytes in the superficial dermis with necrotic keratinocytes at the dermo-epidermal junction. Cutaneous forms usually disappear within 6 to 12 months, but mucous membrane lesions have a more chronic evolution, and can have a malignant potential. The aetiology remains unknown, immunological disorders are probably involved. Local or systemic corticosteroids, retinoids and PUVA therapy are the main treatments, but oral corticotherapy still need to be evaluated.

Epidemiology was initially defined as the study of the distribution of the diseases among the populations (descriptive epidemiology), as well as the identification of the factors which determine this distribution (explicative epidemiology). Now, epidemiology is also interested in the evaluation of the diagnostic and therapeutic procedures and in that of the predictive factors. Epidemiology serves as a guide for public health and medical decisions. The main indicators used in descriptive studies are the prevalence, incidence and mortality rates. Data are collected by systematic reporting or specific surveys. The aim of analytic epidemiology is to ascertain a cause-effect relationship between an exposure and a disease. The strength of the association is estimated by the relative risk or the odds ratio. Other risk estimates are the attributable risk and the etiologic fraction. Interpretation of analytic studies needs to evaluate the role of chance (statistically significant association between the exposure and the disease), the likelihood that the results reflect potential biases or confounding factors, and the causality assessment. Assessing medical strategies implies using the notions of sensitivity, specificity and likelihood ratios. These allow determining the probability a patient has to be hill according to his clinical characteristics and to the results of the examination. Assessing prognostic factors allows estimating the probability of the clinical evolution according to the patients' characteristics.

Dapsone is a sulfone discovered in 1908. Since the 1940s, it is the gold standard in the treatment of leprosy. Dapsone indications have been extended to inflammatory dermatoses and other infections. These indications are based on its antibiotic and immunomodulatory effects. Its bioavailability and half-life characteristics allow single daily dose. Dapsone is metabolised by two enzymatic paths: N-acetylation and N-hydroxylation. The latter may result in dose-related side effects: haemolytic anaemia and methemoglobinaemia. Dapsone is also associated with idiosyncratic side effects (agranulocytosis, hypersensitivity syndrome).

Mycobacterium refers to more than sixty species of which only one quarter is pathogenic; a dozen of species have cutaneous expressions. Environmental (ex-atypical) mycobacteria contract accidentally in the natural surroundings, contrary with the inter-human transmitted mycobacteria which are tuberculosis and leprosy. In France, Mycobacterium marinum-induced lesions of the aquarists are the most frequently reported model of contamination of the immunocompetent subject. In tropical area, Mycobacterium ulcerans infections constitute a real emergent disease for the WHO. Immunodeficiency, in particular that associated with AIDS, supports the generalized forms of mycobacterial diseases, generally related to the Mycobacterium avium-intracellulare complex. Since the development of the tritherapy and cytokines, the frequency of such environmental mycobacteria-induced infections has decreased.

Bourneville tuberous sclerosis complex (BTS) is characterized by hamartomatous lesions that involve skin (hypomelanotic macules, facial angiofibromas, periungueal fibroma), brain (cortical tubers, subependymal nodules), kidney (angiomyolipoma, renal cysts), heart (rhabdomyoma) and eyes. It is an autosomal dominantly inherited disease with 70% of spontaneous mutation. Expression is highly variable even within the same family. Two genes have been identified as causing BTS. TSC1 is found on the long arm of chromosome 9 and TSC2 is situated on the short arm of chromosome 16. Precise clinical and radiological criteria have been identified and recently revised.