Mastocytosis is a rare and heterogeneous disease characterized by an abnormal accumulation of non-malignant mast cells. This excessive number of apparently normal mast cells appears in the skin and, occasionally, in other organs. The most frequent site of organ involvement in patients with any form of mastocytosis is the skin. Urticaria pigmentosa is a subvariant of cutaneous mastocytosis. It is the most common skin manifestation in both adults and children with a good prognosis. We report a case of a 49-year-old woman with a 19-year history of multiple, non-pruritic, hyperpigmented macules and papules on the back, which gradually increased in number to affect the abdomen, chest and extremities.