Urticaria pigmentosa is a skin disease, which is a form of urticaria as well as mastocytosis, in which you find brown, intensely itching patches on the skin. On rubbing the spots, one gets hives or urticarial patches.

It is one of the forms of mastocytosis. To understand mastocytosis, we need to understand a bit about mast cells. Mast cells are normal cells found in the skin all over the body. Mast cells contain certain granules, which, when activated or stimulated, lead to the release of histamine and other such chemicals, leading to the condition called mastocytosis. You may say mast cells are inflammatory cells.

Urticaria pigmentosa is most commonly seen in infants and children but can also be found in adults.

The exact cause of this uncommon disease is unknown but recent research suggests a genetic change in a protein (called c-kit) on the surface of mast cells may result in the abnormal proliferation of these cells.

A variety of factors can cause or worsen the symptoms of urticaria pigmentosa:

A typical presentation called Darier’s sign is observed in Urticaria pigmentosa. By rubbing one of the brown patches, the rubbed area becomes reddened, swollen, and itchy. This confirms the presence of mastocytosis