 The purpose of this study is to explore the key symptoms of individuals with systemic mastocytosis. Interviews of enrolled individuals will be conducted to learn about the disease symptoms and condition. The interview will last approximately 60 minutes and will be conducted by a trained interviewer, be audio-recorded with patient consent, and all information provided by the patient will be treated confidentially and made anonymous so that it is non-identifiable. The interview may be conducted face-to-face, over the phone, or virtually via Skype, a free video conferencing program, depending upon the patients geographic location. Patients will be compensated for their participating time. 