Mastocytosis: A condition characterized by infiltration of mast cells into the tissues of the body. Mast cells are connective tissue cells which release chemicals including histamine that are very irritating and cause itching, swelling, and fluid leakage from cells.
There are several different clinical forms of mastocytosis, including:
- Mastocytoma -- A benign nodular tumor on the skin rich in mast cells. Usually present at birth or in early childhood and resolves spontaneously. Also called a mast cell tumor.
- Urticaria pigmentosa -- The most common form of mastocytosis consisting of small aggregations of mast cells within characteristic salmon-brown patches of ski which itch when stroked and be filled with fluid. The condition occurs occurring primarily in children and clears spontaneously with adolescence.
- Telangiectasia perstans -- A form of mastocytosis that usually affects adults, characterized by the presence of multiple hyperpigmented macules with telangiectases (visibly dilated small blood vessels), located primarily on the trunk, but also on the extremities.
- Diffuse mastocytosis (also called diffuse cutaneous mastocytosis) -- The entire skin is thickened and leathery with generalized reddening and intense pruritus (itching) due to widespread infiltration of the skin with mast cells.
- Systemic mastocytosis -- Characterized by mast cell infiltrates in skin, lymph nodes, liver, spleen, gastrointestinal tract, bones, and joints with a predisposition to peptic ulcer (due to excess stomach acid caused by the histamine).