[1] 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.

[2] 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.

[6] Mast cells are located in connective tissue, including the skin, the linings of the stomach and intestine, and other sites.

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.

In cases of suspicion of SM help can also be drawn from analysis of mutation in KIT(D816V) in peripheral blood using sensitive PCR-technology[citation needed] To set the diagnosis of systemic mastocytosis, certain criteria must be met.

Quantitative mast cell stains may yield little diagnostic information, and further research studies are warranted to determine whether "mastocytic enterocolitis" truly represents a distinct entity.

[20] Allogeneic stem cell transplantation has been used in rare cases with aggressive systemic mastocytosis in patients deemed to be fit for the procedure.

The prognosis for patients with advanced systemic mastocytosis differs depending on type of disease with MCL being the most serious form with short survival.

NIH scientists have identified some mutations, which may help researchers understand the causes of mastocytosis, improve diagnosis, and develop better treatments.