<qa>  What is anaphylaxis associated with?Anaphylaxis is a serious allergic reaction that develops rapidly and can cause death. Some patients experience anaphylaxis is association with exercise, a disorder called exercise-induced anaphylaxis. A subset of patients with unexplained anaphylaxis, especially those with hypotension during the anaphylactic episodes, have been shown to have abnormal, clonal populations of a certain cell type, mast cells, in the bone marrow. This has been described in at least one patient with exercise-induced anaphylaxis. The investigators would like review the findings in a group of patients with exercise-induced anaphylaxis who have undergone evaluation for the presence of abnormal, clonal mast cells. 