RT Book, Section A1 Akin, Cem A1 Boyce, Joshua A. A2 Jameson, J. Larry A2 Fauci, Anthony S. A2 Kasper, Dennis L. A2 Hauser, Stephen L. A2 Longo, Dan L. A2 Loscalzo, Joseph SR Print(0) ID 1155952409 T1 Mastocytosis T2 Harrison's Principles of Internal Medicine, 20e YR 2018 FD 2018 PB McGraw-Hill Education PP New York, NY SN 9781259644016 LK accesspharmacy.mhmedical.com/content.aspx?aid=1155952409 RD 2024/04/18 AB Mastocytosis is defined by accumulation of clonally expanded mast cells in tissues such as skin, bone marrow, liver, spleen, and gut. The mast cell expansion is generally recognized in skin and/or bone marrow. Mastocytosis occurs at any age and has a slight preponderance in males. Mastocytosis is a rare disorder and its exact prevalence is not known; however, it is estimated to occur in ~1 in 20,000 people. Familial occurrence is rare, and atopy is not increased compared to the general population.