The c-kit Asp816Val activating mutation is found in all patients with mastocytosis with an associated hematologic disorder, and at least in a subset of patients with indolent mastocytosis. The case of an 11-month-old child is presented who was categorized as having indolent mastocytosis, and where the Asp816Val mutation was identified in lesional skin, but not in bone marrow or in peripheral blood mononuclear cell populations. The significance of these findings is discussed.