[Urticaria pigmentosa: two different clinical presentations in pediatric patients].

Urticaria pigmentosa (UP) is the most frequent clinical feature of cutaneous mastocytosis. It usually begins in a bimodal way: a peak of incidence from birth to the age of 3 and the other one between 2(nd) and 6(th) decades of life. Darier's sign is constant over the affected skin without affecting the surrounding skin. When UP starts early, it has a good prognosis disappearing into adolescence, while late onset is often associated with persistent or systemic involvement. This article reports two cases of UP, one with the classic description of the disease and the other with an unusual clinical presentation, prompting the pediatrician to incorporate both forms as different manifestations of the same entity.