Allergy
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Patients with elevated basal tryptase (sBT) >15 μg/l and anaphylaxis may have an underlying mastocytosis. A monoclonal mast cell activation syndrome with aberrant mast cells (MC) at extracutaneous sites has been described in patients with severe hypotension or anaphylaxis. ⋯ We could show for the first time that the normal skin can harbour clonal MC in anaphylaxis patients. Analogous to the criteria for mastocytosis, we suggest a skin score criteria including an elevated number of MC, spindle shape, CD25 expression, c-Kit mutation and sBT values >20 μg/l. In patients with anaphylaxis and elevated sBT, skin should be biopsied and, as with the approach for mastocytosis diagnosis in the bone marrow, MC should be analysed for their number, clonality and c-Kit mutation. This approach should be confirmed in further studies. Patients with aberrant skin MC should be handled as mastocytosis patients.