Page 1 of 5
Close concept: urtikariya
The small tortoiseshell — vascular reaction which is clinically characterized quickly arising, raised over the skin surface, hyperemic sites of hypostasis of rounded shape taking derma blankets. In these sites which are often called by blisters the itch usually is felt. Separate elements arise suddenly and are most often resolved during 24 h.
Quincke's disease call deeper reaction which arises if hypostasis takes a derma and gets into hypodermic or submucosal fabric. The Quincke's disease most often meets on a face and extremities, often is followed by the small tortoiseshell though can arise and independently. At inspection of 554 patients with a Quincke's disease or the small tortoiseshell only the urtikariya is found in 40%, only the Quincke's disease is found in 11%, and both states are found in 49%.
The small tortoiseshell usually call chronic if elements arise daily and such state proceeds more than 4 weeks. However Akers and Naversen carry to a chronic urtikariya cases in which emergence of fresh elements manages to be found at least within 4 days a week, and the disease proceeds 8 weeks.
Prevalence of the small tortoiseshell
The small tortoiseshell people of any gender, races, age and a profession are surprised. Consider that approximately at 15 — 20% of population ever in life the small tortoiseshell was marked out. Frequency makes it 0,11% at men and women have 0,14%. The acute small tortoiseshell is most often observed at young people, chronic at women of middle age.
The small tortoiseshell can be caused by various reasons and be implemented for the account of both immunological, and not immunological factors. The mechanisms which are the cornerstone of the small tortoiseshell thoroughly are not investigated, but consider that final stages of the general pathophysiological process include activation of mast cells and basphilic leukocytes. These cells in the course of activation allocate mediators which increase permeability of vessels. At the expense of it sweating of plasma through walls of vessels in a derma and formation of elements of an urtikariya begins.
One of immunologic mechanisms of the small tortoiseshell is reaction of immediate hypersensitivity (or type I) which central element are IgE-antibodies. IgE are produced by V-lymphocytes and plasmocytes in response to effect of antigens which include proteins, polysaccharides and haptens. IgE can communicate mast cells and basophiles by means of Fc-receptors. Then, in process of stimulation antigen in the course of which antigen connects at least two molecules IgE on a surface of mast cells of silt of basophiles from these cells allocates numerous biologically active products. These products are discussed below. (The biochemical mechanisms causing allocation of mediators are described in detail in the corresponding works.)
The small tortoiseshell can be called by immunologic mechanisms which do not require IgE. Interaction of antigens with IgG or IgM can allow the classical cascade of complement activation as a result of which SZA anaphylotoxins and S5a which in itself can cause allocation of a histamine from mast cells and basophiles (the II type) are produced. The alternative way of complement activation can cause also degranulation of mast cells due to influence of agents like endotoxins and inulin on secretion of SZA and S5a.
Some cases of an urtikariya, for example, an urtikarny vasculitis, are caused by reaction of hypersensitivity of the III type — the circulating cell-bound immune complexes. Cell-bound immune complexes are the units of antigens, antibodies and a complement which are formed in a circulatory bed or in fabrics. Cell-bound immune complexes can interact with a vascular wall or with other fabrics, causing damage at the expense of complement activation and inflow of neutrophils that is shown in <a type of the morphological picture called by a leykotsitoklastichesky vasculitis.
Along with immunologic mechanisms many chemicals are capable to cause allocation of a histamine from mast cells and basophiles due to direct pharmacological action which as believe, is not connected with immunological processes. Amines, codeine, morphine, a curare, quinine, thiamin, acetylsalicylic acid and a number of new non-steroidal anti-inflammatory drugs belong to these chemicals.
Physical factors, for example heat, cold, light and vibration, can also cause allocation of a histamine and an urtikariya. In these cases allocation of a histamine and other mediators can arise as due to immunological, and not immunological processes or at the expense of their combination.
In process of activation of mast cells and basophiles the set of the mediators causing the small tortoiseshell is allocated. The histamine and slowly operating substance of an anaphylaxis (SRS-A) cause a relaxation of smooth muscles and increase permeability of a vascular wall. SRS-A also promotes formation of prostaglandins, and metabolites of arachidonic acid like prostaglandins and leukotrienes increase vascular permeability, exert impact on contractility of smooth muscles, strengthen a chemotaxis of eosinophils and neutrophils. An eosinophilic chemotactic factor of an anaphylaxis (ECF-A), ECF олигопептиды, lipidic chemotactic factors and a high-molecular neutrophylic chemotactic factor (HMW-NCF) are produced by mast cells and basophiles, they cause hemotaksichesky adhesion or deactivation of eosinophils or neutrophils.
The histologic picture of a separate element of an urtikariya usually includes: derma hypostasis, expansion and swelling of blood vessels, the moderate polymorphic perivascular infiltration consisting generally of lymphocytes and not numerous eosinophils. These signs are more expressed in middle and upper part of a derma. At angionevroticheeky hypostasis first of all sublayers of a derma and hypodermic fabric are surprised. The histologic picture of defeats at the urtikariya caused by a vasculitis differs from other types of the small tortoiseshell. Urtikariya at a vasculitis is characterized morphologically by hypostasis of an endothelium of blood vessels, leykotsitoklazisy (disintegration of neutrophils), fibrinoid deposits in a wall of vessels and around it, emigration of erythrocytes, a perivascular leukocytic infiltration.