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Mastocytosis, one of the ''mast cell diseases'', is a rare mast cell activation disorder of both children and adults caused by the presence of too many mast cells (''mastocytes'') and CD34+ mast cell precursors. People affected by mastocytosis are susceptible to itching, hives, and anaphylactic shock, caused by the release of histamine from mast cells. The current classifications, definitions and diagnostic criteria for mastocytosis are being reviewed for revision to better describe the collection of related disorders.〔http://www.mastocytosis.ca/masto.htm〕 == Classification == Mastocytosis can occur in a variety of forms: * Most cases are cutaneous (confined to the skin only), and there are several forms. The most common cutaneous mastocytosis is urticaria pigmentosa (UP), more common in children, although also seen in adults. Telangiectasia macularis eruptiva perstans (TMEP) is a much rarer form of cutaneous mastocytosis that affects adults. UP and TMEP can evolve into indolent systemic mastocytosis. This should be considered if patients develop any systemic symptoms . * Systemic mastocytosis involves the bone marrow in some cases and in some cases other internal organs, usually in addition to involving the skin. Any organ can be involved. Mast cells collect in various tissues and can affect organs where mast cells do not normally inhabit such as the liver, spleen and lymph nodes, and organs which have normal populations but numbers are increased. In the bowel, it may manifest as mastocytic enterocolitis. There are three classes of systemic mastocytosis: indolent systemic mastocytosis, aggressive systemic mastocytosis, and Leukemic systemic (which affects 3% of cases). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mastocytosis」の詳細全文を読む スポンサード リンク
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