Mastocytosis

Mastocytosis is a group of disorders in which abnormal numbers of mast cells accumulate in the skin, bone marrow, or other organs. It ranges from skin-limited disease to systemic forms that can affect multiple organs.

Mast cell: A tissue-resident immune cell that releases histamine and other mediators during allergic and inflammatory responses. Mastocytosis involves abnormal accumulation of this cell type.
KIT D816V: An activating mutation in KIT found in many cases of systemic mastocytosis. It promotes mast-cell survival and proliferation in a large share of systemic cases.
Mastocytosis diagnostic criteria: A set of tissue, molecular, and laboratory findings used to classify systemic mastocytosis. The criteria distinguish clonal disease from isolated symptoms or elevated tryptase.
Mast-cell activation syndrome: A disorder defined by recurrent episodes of systemic mast-cell mediator release and associated symptoms. It involves abnormal activation, not necessarily the clonal mast-cell accumulation that defines mastocytosis.
Histamine: A signaling molecule involved in allergic reactions, inflammation, and regulation of stomach acid. Mast-cell mediator release can cause itching, flushing, and gastrointestinal symptoms.
Stem cell factor: A cytokine that binds KIT and supports mast-cell development, survival, and function. Its receptor pathway is altered by common KIT mutations in mastocytosis.
Darier's sign: A wheal-and-flare reaction caused by rubbing a mastocytosis skin lesion. This characteristic skin response can help identify cutaneous disease.
Hereditary alpha tryptasemia: An inherited trait caused by increased TPSAB1 copy number that commonly raises baseline serum tryptase. It can mimic a mast-cell-burden marker without being mastocytosis.
KIT (receptor): A cell-surface receptor tyrosine kinase activated by stem cell factor and involved in cell survival and development. Activating KIT mutations drive many cases of systemic mastocytosis.
Tryptase: A protease stored in mast-cell granules and released during mast-cell activation. Persistently elevated baseline serum tryptase can indicate increased mast-cell burden.

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Darier diseaseCompared with: Its lesions can show Darier sign, a finding unrelated to the inherited disease named Darier.