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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.


Severe form of diffuse cutaneous mastocytosis in an infant.


Thickening of the palms in an infant with diffuse cutaneous mastocytosis.


Multiple mastocytomas on the back of an adult man.

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

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-1 WHO Classification of Mastocytosis

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

Rare; approximately 1-4:10,000 live births.

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).

History of recurrent flushes, urticarial wheals, pruritus, dizziness, and headaches. Darier sign is pathognomonic and is defined as development of an ...

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