Also found in: Dictionary, Encyclopedia, Wikipedia.




Mastocytosis is a disease characterized by the presence of too many mast cells in various organs and tissues.


The body has a variety of free-roaming cell populations that function as immunogenic agents. Most immunogenic cells fall into the category of white blood cells, but some remain in tissues and are not found in the blood. Mast cells are such a group.
Mast cells are found primarily in the skin and digestive system, including the liver and spleen, and produce histamine, a chemical most famous for its ability to cause itching. Histamine also causes acid indigestion, diarrhea, flushing, heart pounding, headaches, and can even cause the blood pressure to drop suddenly.
Mastocytosis comes in three forms. Most cases produce symptoms but do not shorten life expectancy. The three forms are:
  • Mastocytoma, a benign skin tumor.
  • Urticaria pigmentosa, small collections of mast cells in the skin that manifest as salmon or brown-colored patches.
  • Systemic mastocytosis, the collection of mast cells in the skin, lymph nodes, liver, spleen, gastrointestinal tract, and bones.

Causes and symptoms

The cause of mastocytosis is unknown. People with systemic mastocytosis have bone and joint pain. Peptic ulcers are frequent because of the increased stomach acid stimulated by histamine. Many patients with systemic mastocytosis also develop urticaria pigmentosa. These skin lesions itch when stroked and may become fluid-filled.


A biopsy of the skin patches aids diagnosis. An elevated level of histamine in the urine or blood is also indicative of mastocytosis.


Mastocytoma usually occurs in childhood and clears-up on its own. Urticaria pigmentosa (present alone without systemic disease) also dramatically clears or improves as adolescence approaches.
Several medications are helpful in relieving symptoms of systemic mastocytosis. Antihistamines and drugs that reduce stomach acid are frequently needed. Headaches respond to migraine treatment. A medicine called cromolyn helps with the bowel symptoms. Several other standard and experimental medications have been used.


Mastocytoma and urticaria pigmentosa rarely if ever, develop into systemic mastocytosis, and both spontaneously improve over time. Systemic mastocytosis is only symptomatically treated. There is no known treatment that decreases the number of mast cells within tissue.



Austen, K. Frank. "Diseases of Immediate Type Hypersensitivity." In Harrison's Principles of Internal Medicine, edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1997.

Key terms

Non-steroidal anti-inflammatory drugs (NSAIDs) — Aspirin, ibuprofen, naproxen, and many others.
Peptic ulcer — Ulcers in the stomach and upper duodenum (first portion of the small intestine) caused by stomach acid and a bacterium called Helicobacter pylori.


an accumulation, local or systemic, of mast cells in the tissues; known as urticaria pigmentosa when widespread in the skin.
diffuse mastocytosis (diffuse cutaneous mastocytosis) a condition in which the entire skin is thickened, lichenified, and leathery in appearance and accompanied by generalized erythroderma and intense pruritus as a result of widespread infiltration with mast cells. In children, it is often associated with systemic mastocytosis.
systemic mastocytosis a condition in which there are mast cell infiltrates in noncutaneous tissues, occurring with or without cutaneous lesions, and usually involving the liver, spleen, bone, lymph nodes, and gastrointestinal tract.


Abnormal proliferation of mast cells in a variety of tissues; may be systemic, involving a variety of organs, or cutaneous (urticaria pigmentosa).
[mastocyte + G. -osis, condition]


/mas·to·cy·to·sis/ (-si-to´sis) an accumulation, local or systemic, of mast cells in the tissues; known as urticaria pigmentosa when widespread in the skin.


Etymology: Ger, Mast, fattening; Gk, kytos, cell, osis, condition
local or systemic overproduction of mast cells, which in rare instances may infiltrate liver, spleen, bones, the GI system, and skin. Systemic mastocytosis may precede mast cell leukemia.


A heterogeneous group of uncommon, poorly understood lesions characterised by increased mast cells in one or more tissues or organs, especially skin. Mastocytosis may be classified according to extent and behaviour.

Mastocytosis classifications
▪ Localised mastocytosis:
   – Focal—single skin lesion: mast cell “naevus”;
   – Generalised—urticaria pigmentosa.
 ▪ Systemic mastocytosis:
   – Indolent;
   – Progressive;
   – Malignant.
▪ Mast cell leukaemia.
▪ Mast cell sarcoma.
Some cases may be reactive to increased soluble mast cell growth factor (c-kit-ligand), possibly due to an increase in proteolytic processing (a cytokine that causes mast cell accumulation), melanocyte proliferation and increased melanin production.


A heterogeneous group of uncommon, poorly understood lesions characterized by ↑ mast cells in one or more tissues or organs, especially skin; mastocytosis may be classified according to extent and behavior. See Mast cell leukemia. Urticaria pigmentosa
Localized mastocytosis
• Focal: Single skin lesion: mast cell 'nevus'
• Generalized: Urticaria pigmentosa
Systemic mastocytosis
• Indolent
• Progressive
• Malignant
Mast cell leukemia
Mast cell sarcoma
Pathogenesis Some cases may be reactive to ↑ soluble mast cell growth factor–kit-ligand, possibly due to an ↑ in proteolytic processing, a cytokine that causes mast cell accumulation, melanocyte proliferation and ↑ melanin production NEJM 1993; 328:1302oa Reactive mastocytosis A focal ↑ in mast cells due to immediate or delayed hypersensitivity reactions, which may also occur in lymph nodes draining benign or malignant lesions, eg chronic liver or renal disease, leukemia, lymphoproliferative disorders or Hodgkin's disease; benign mast cell diseases include localized mastocytosis, which may be cutaneous or extracutaneous and urticaria pigmentosa Systemic mastocytosis A potentially aggressive condition characterized by mast cell proliferation in the skin, liver, lymph nodes, BM, GI tract Clinical Histamine hyperproduction with flushing, vertigo, palpitations, pruritus, colic, dyspnea, nausea; Sx range from mild and intermittent, to severe, disabling, and progressive 'Malignant' systemic mastocytosis A form of mast cell disease that is fatal within 2 years of conversion to an aggressive form  


Abnormal proliferation of mast cells in a variety of tissues; may be systemic, involving various organs, or cutaneous (urticaria pigmentosa).
[mastocyte + G. -osis, condition]


An excessive proliferation of MAST CELLS in the tissues or in the bone marrow.


an accumulation, local or systemic, of mast cells in the tissues. Occurs in horses of all ages where the lesions disappear spontaneously from the skin but the nodules are present for about a year. See also mast cell tumor.

systemic mastocytosis
see mast cell leukemia.
References in periodicals archive ?
Diffuse cutaneous mastocytosis is a rare type of mastocytosis which occurs in childhood.
Systemic mastocytosis is related to a constitutively activated receptor tyrosine kinase encoded by the KIT D816V mutation.
Cutaneous and systemic manifestations of mastocytosis.
This case report describes the presentation of a cutaneous mast cell tumor with secondary self-mutilation and disseminated mastocytosis in an adult female lovebird.
Systemic mastocytosis represents a heterogenous group of disorders characterised by abnormal accumulation of mast cells in a variety of tissues including the skin and bone marrow.
Global Markets Direct's, 'Systemic Mastocytosis - Pipeline Review, H2 2012', provides an overview of the indication's therapeutic pipeline.
In April, Rydapt was approved in the US for the treatment of newly diagnosed FLT3-mutated AML and three types of systemic mastocytosis (SM).
If approved, Rydapt will be the first targeted treatment available in the European Union (EU) for newly diagnosed FLT3 mutation-positive AML patients and advanced systemic mastocytosis (SM) patients.
UP can rarely progress to systemic mastocytosis and present with systemic symptoms that are more common in adults, including headache, fatigue, abdominal pain, diarrhea, and tachycardia.
2] Malabsorption Including celiac disease Mastocytosis Bone pain, fractures Monoclonal gammopathies Multiple myeloma; abnormal immunoglobulin protein Organ transplantation Immunosuppressive drugs Osteogenesis imperfecta Positive collagen type I genetic test Primary hyperparathyroidism Hypercalcemia; elevated parathyroid hormone Tobacco use Current smoker BMD, bone mineral density; BMI, body mass index; Ca, calcium; GFR, glomerular filtration rate; HIV, human immunodeficiency virus; LFT, liver function tests; RA, rheumatoid arthritis.
A patient with mastocytosis, a group of disorders characterized by pathologic mast cells infiltrating the skin, will consistently have elevated tryptase levels.