Urticaria Pigmentosa (Cutaneous Mastocytosis)

Mastocytosis is a disorder characterized by mast cell accumulation, commonly in the skin, bone marrow, gastrointestinal (GI) tract, liver, spleen, and lymphatic tissues. The World Health Organization (WHO) divides cutaneous mastocytosis into three main presentations. The first has solitary or few (less than or equal to 3) lesions called "mastocytomas." The second involves multiple lesions ranging from less than 10 to greater than 100 which is referred to as "urticaria pigmentosa" (UP). The last presentation involves diffuse cutaneous involvement. Urticaria pigmentosa is the most common cutaneous mastocytosis in children, and it can form in adults as well. It is thought to be a benign, self-resolving condition that remits in adolescence. Unlike adult forms of mastocytosis, there is rarely any internal organ involvement in UP.[1]