Correct!
4. 1 and 3

We suspected the patient’s attacks represented acute degranulation events associated with systemic mastocytosis (SM). Systemic mastocytosis, as the name implies, occurs when dysregulated proliferation of mast cells leads to systemic symptoms. Our patient had urticaria pigmentosa which is characterized by red or brown papules that represent aggregates of mast cells in the skin. The mast cells, when irritated (e.g. by rubbing the skin, heat exposure), degranulate histamine, leukotrienes, and other mediators, triggering an urticarial skin reaction sometimes referred to as Darier's sign. In Figure 1 note the erythematous wheals on upper abdomen elicited by stroking skin. Derriere is French for buttocks.

Which of the following would support a diagnosis of systemic mastocytosis?

1. An elevated tryptase level
2. Increased mast cells in the bone marrow and/or skin
3. Increased expression of CD25 on the mast cells
4. The D816/KIT mutation of the stem cell factor receptor
5. All of the above

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