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Accumulation and degranulation of mast cells
(mastocytosis) in the skin or other organs. A group of disorders
characterized by accumulation of mast cells in the skin with or without
other organ system involvement. Systemic mastocytosis occurs in
approximately 10% of all cases, with proliferation of mast cells in other
tissues such as bone, liver, and spleen.
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Mast Cell Disease;
Systemic Mast Cell Disease (SMCD).
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A classification of mastocytosis has been proposed
based on clinical presentation and prognosis (see the WHO Classification of
Mastocytosis in Table M-1).
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The cutaneous manifestation, urticaria pigmentosa, is the
most common form and was first described in 1869.
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Rare; approximately 1-4:10,000 live births.
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Usually not considered an inherited disease,
although there is some evidence of an autosomal dominant pattern in the
diffuse cutaneous form. Males and females are affected equally.
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There is an excess of mast cells in body tissues,
and the clinical expression of the disorder depends upon the pattern of
localization of the mast cells to specific organs. Dysregulation of
production and function of mast cells is caused by distinct mutations in
c-Kit, a type III transmembrane tyrosine kinase. Mediator release by mast
cells may occur spontaneously or be triggered by a variety of stimuli. These
biochemical substances include histamine and heparin, thought to be the most
important, and other enzymes such as chymases, tryptases, and hydrolases.
Prostaglandin D2, cytokines (tumor necrosis factor [TNF]-α and
TNF-β, interleukin [IL]-3, IL-5, and IL-16), serotonin, leukotrienes,
and platelet-activating factor are also released. Among the precipitating
factors are trauma, surgery, extremes of temperature, toxins, alcohol, and a
variety of drugs (including acetylsalicylic acid, morphine, codeine,
thiopentone, lignocaine, gallamine, and d-tubocurarine).
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History of recurrent flushes, urticarial wheals,
pruritus, dizziness, and headaches. Darier sign is pathognomonic and is
defined as development of an ...