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At a glance

It is a medical condition that leads to accumulation and degranulation of mast cells (mastocytosis) in the skin, bone marrow, liver, spleen, gastrointestinal tract, and lymph nodes. Systemic mastocytosis occurs in approximately 10% of all cases. There are seven subtypes of this disorder based on the clinical presentation, the onset of the symptoms, and the prognosis (see below). The frequency of perioperative anaphylaxis appears to be higher in mastocytosis patients than in the general population.


Mast Cell Disease; Systemic Mast Cell Disease (SMCD); Pigmentary Urticaria.


A classification of mastocytosis has been proposed based on clinical presentation and prognosis (see the WHO Classification of Mastocytosis in Table M-1).

TABLE M-1WHO Classification of Mastocytosis


The cutaneous manifestation, urticaria pigmentosa, is the most common form and was first described in 1869.


The exact incidence has not been determined. It affects males and females equally. It is not classified as an allergic disorder but a rare medical condition. Its incidence is estimated incidence of 1:150,000 live births in the general population. The most frequent being the Cutaneous Form, called the urticaria pigmentosa or maculopapular cutaneous mastocytosis.

Genetic inheritance

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.


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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