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).