Systemic mastocytosis

Mastocytosis, a type of mast cell disease, is a rare disorder affecting both children and adults caused by the accumulation of functionally defective mast cells (also called mastocytes) and CD34+ mast cell precursors.see also Template:Congenital malformations and deformations of skin appendages, Template:Phakomatoses, Template:Pigmentation disorders, Template:DNA replication and repair-deficiency disorder Mastocytosis, a type of mast cell disease, is a rare disorder affecting both children and adults caused by the accumulation of functionally defective mast cells (also called mastocytes) and CD34+ mast cell precursors. People affected by mastocytosis are susceptible to a variety of symptoms, including itching, hives, and anaphylactic shock, caused by the release of histamine and other pro-inflammatory substances from mast cells. When mast cells undergo degranulation, the substances that are released can cause a number of symptoms that can vary over time and can range in intensity from mild to severe. Because mast cells play a role in allergic reactions, the symptoms of mastocytosis often are similar to the symptoms of an allergic reaction. They may include, but are not limited to Mast cells are located in connective tissue, including the skin, the linings of the stomach and intestine, and other sites. They play an important role in the immune defence against bacteria and parasites. By releasing chemical 'alarms' such as histamine, mast cells attract other key players of the immune defense system to areas of the body where they are needed. Mast cells seem to have other roles as well. Because they gather together around wounds, mast cells may play a part in wound healing. For example, the typical itching felt around a healing scab may be caused by histamine released by mast cells. Researchers also think mast cells may have a role in the growth of blood vessels (angiogenesis). No one with too few or no mast cells has been found, which indicates to some scientists we may not be able to survive with too few mast cells. Mast cells express a cell surface receptor, c-kit (CD117), which is the receptor for stem cell factor (scf). In laboratory studies, scf appears to be important for the proliferation of mast cells. Mutations of the gene coding for the c-kit receptor (mutation KIT(D816V)), leading to constitutive signalling through the receptor is found in >90% of patients with systemic mastocytosis. Diagnosis of urticaria pigmentosa (cutaneous mastocytosis, see above) can often be done by seeing the characteristic lesions that are dark-brown and fixed. A small skin sample (biopsy) may help confirm the diagnosis.