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Mastocytosis is a topic covered in the 5-Minute Clinical Consult.

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Mastocytosis is a rare, heterogeneous group of disorders caused by the abnormal clonal proliferation and accumulation of atypical mast cells in one or more organs of the body, most often affecting the skin.


  • Two clinical diagnostic categories: cutaneous mastocytosis (CM) or systemic mastocytosis (SM)
  • CM only is the most common form, whereas SM constitutes only 10–15% of all the cases.
  • CM consistency primarily of skin involvement with characteristic lesions, urticaria pigmentosa (UP)
  • Symptoms of mastocytosis are from mast cell degranulation and release of chemical mediators, such as histamine, leukotrienes, and prostaglandins.
  • In adults, mastocytosis often is secondary to a gain-of-function point mutation in the proto-oncogene c-kit (D816V in >95% of cases) leading to clonal proliferation of mast cells.
  • Childhood mastocytosis is associated with c-kit, D816V in only 40% of cases; majority of cases are limited to the skin and have excellent prognosis with spontaneous resolution around puberty.


  • Incidence and prevalence will vary because many cases remain undiagnosed.
  • Prevalence estimated 1 in 60,000 people.
  • Incidence 0.1 to 1/100,000 people per year in United States
  • ~2/3 of reported CM cases are found in children, most diagnosed before the age of 2 years.
  • Adults more likely to have systemic disease and onset between 20 and 50 years with diagnosis at 40 to 60 years
  • Prevalence equal in males and females

Etiology and Pathophysiology


The disease is congenital in 15–25% of cases.

  • Gain-of-function point mutations in c-kit, in particular D816V
    • C-kit (KIT) is a proto-oncogene that encodes for a tyrosine kinase receptor (CD117 transmembrane receptor) located on many hematopoietic stem cells, including mast cells.
    • Normally, stem cell factor (SCF) binds to CD117 leading to mast cell growth, migration, survival.
    • Autophosphorylation of tyrosine residues in the presence of gain-of-function c-kit mutations leads to unregulated proliferation of mast cells.
    • Mutations in other genes may also be pathogenic in some cases.
    • There is no known genetic transmission.

Risk Factors

Age; c-kit–activating mutations

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Stephens, Mark B., et al., editors. "Mastocytosis." 5-Minute Clinical Consult, 27th ed., Wolters Kluwer, 2019. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/816314/5/Mastocytosis.
Mastocytosis. In: Stephens MB, Golding J, Baldor RA, et al, eds. 5-Minute Clinical Consult. 27th ed. Wolters Kluwer; 2019. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/816314/5/Mastocytosis. Accessed July 15, 2019.
Mastocytosis. (2019). In Stephens, M. B., Golding, J., Baldor, R. A., & Domino, F. J. (Eds.), 5-Minute Clinical Consult. Available from https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/816314/5/Mastocytosis
Mastocytosis [Internet]. In: Stephens MB, Golding J, Baldor RA, Domino FJ, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2019. [cited 2019 July 15]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/816314/5/Mastocytosis.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Mastocytosis ID - 816314 ED - Stephens,Mark B, ED - Golding,Jeremy, ED - Baldor,Robert A, ED - Domino,Frank J, BT - 5-Minute Clinical Consult, Updating UR - https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/816314/5/Mastocytosis PB - Wolters Kluwer ET - 27 DB - Medicine Central DP - Unbound Medicine ER -