Paul Ehrlich first described mast cells in 1877 on the basis of their unique staining characteristics and large granules. Mast cells are part of the body's immune system. Mast cells are very similar to basophil granulocytes (type of white blood cell), which are both thought to originate from bone marrow precursors expressing the CD34 molecule. The basophil leaves the bone marrow once it is mature. The mast cells, on the other hand, circulate in an immature form until they reach tissue, where they fully develop.
Mast cells are found in most tissues that are near blood vessels. They are especially prominent in the skin, mucosa of the lungs and digestive tract, as well as the mouth, conjunctiva and nose.
In the early to mid-20th Century, all forms of mast cell disease were categorized under the group referred to as mastocytosis, which is characterized by abnormal mast cell growth. Over the last 30 years, researchers have defined several different categories, and the current definitions are still evolving.
Mast cell disease is more common among children than adults. According to research, the onset of mastocytosis occurs in children younger than two years old in 55% of patients.
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main types of mastocytosis
Cutaneous mastocytosis (urticaria pigmentosa): When mast cells build up in the skin, the condition is known as cutaneous mastocytosis. Skin lesions, called urticaria pigmentosa, are present in most patients with cutaneous mastocytosis. This condition primarily affects children and resolves as children reach puberty in more than 50% of pediatric cases. Symptoms usually decrease in the remaining patients as they mature into adults. The disease may progress to the more serious systemic mastocytosis in adults. When the mast cells cause a single lesion on the skin, it is known as solitary mastocytoma.
Mastocytoma (mast cell tumor): A mastocytoma is a benign skin tumor consisting of mast cells. Mastocytoma is usually present at birth or in early childhood, and in most cases, it spontaneously resolves. While this condition can occur in humans, it is seen most often in dogs and cats.
Systemic mastocytosis: Systemic mastocytosis is a rare disorder characterized by abnormal accumulations of mast cells throughout the body, especially in the bone marrow and internal organs. This form of the disease primarily affects adults. Systemic mast cell disease has been associated with several other hematologic diseases, including hypereosinophilic syndrome, Castleman disease, monoclonal gammopathy and hairy cell leukemia. Non-Hodgkin lymphoma, polycythemia vera and primary thrombocythemia have also been associated with systemic mastocytosis. While the specific incidence of systemic mastocytosis remains unknown, some studies in Great Britain reported an average of only two new cases per year, from a study population of 300,000.