Mastocytosis.

Mastocytosis is a group of rare disorders of both children and adults caused by the presence of too many mast cells  and CD34+ mast cell precursors in a person's body.Doctors can diagnose urticaria pigmentosa  by seeing the characteristic lesions that are dark-brown and fixed. A small skin sample (biopsy) may help confirm the diagnosis.
By taking a biopsy from a different organ, such as the bone marrow, the doctor can diagnose systemic mastocytosis. Using special techniques on a bone marrow sample, the doctor looks for an increase in mast cells. Another sign of this disorder is high levels of certain mast-cell chemicals and proteins in a person's blood and sometimes in the urine.No one is sure how many people have either type of mastocytosis, but mastocytosis generally has been considered to be an "orphan disease" (orphan diseases affect 200,000 or fewer people in the United States). Mastocytosis, however, often may be misdiagnosed, especially because it typically occurs secondary to another condition, and thus may occur more frequently than assumed.National Institute of Allergy and Infectious Diseases scientists have been studying and treating patients with mastocytosis for several years at the National Institutes of Health (NIH) Clinical Center.
Some of the most important research advances for this rare disorder include improved diagnosis of mast cell disease and identification of growth factors and genetic mechanisms responsible for increased mast cell production. Researchers are currently evaluating approaches to improve ways to treat mastocytosis.
Scientists also are focusing on identifying disease-associated mutations . NIH scientists have identified some mutations, which may help researchers understand the causes of mastocytosis, improve diagnosis, and develop better treatments.Scientists first described urticaria pigmentosa in 1869. Systemic mastocytosis was first reported by French scientists in 1936.