Mastocytosis & Mast Cell Disorders Definition Signs & Symptoms Diagnosis Treatment Symptom Management Related Conditions FAQ
In Canada, 1 in 12 people live with a diagnosed rare disorder1. There are approximately 7,000 types of rare disorders documented in Canada.2 This translates to nearly 3 million Canadians diagnosed with a rare disorder, one of which is Mastocytosis. These numbers do not include countless Canadians suffering without a diagnosis. To put this in some perspective, our organization is aware of approximately 300 people of all ages in Canada diagnosed with a form of mastocytosis.

Mastocytosis is a rare disorder (or disease). Medical research articles alternate between classifying it as a "disorder" or a "disease", depending on the researchers' focus on the various forms or types of mastocytosis. We refer to it as both alternately in an effort to be inclusive for all patients, regardless of type, form, variant or subvariant named within the mastocytosis definitions.

Mastocytosis and Mast Cell Activation Sydrome affect all systems, organs and tissues of the body. In particular, skin, liver, spleen, lymph nodes, bones and bone marrow, lungs, gastrointestinal system, eyes and blood are the most documented as adversely impacted by these diseases. Research exists but much more needs to be done to further identify and understand the less studied effects of mast cell disorders on the heart, brain and female reproductive system.

Despite mastocytosis & related mast cell disorders being classified as rare, escalation in the prevalence of these patients worldwide has resulted in a flurry of medical research ongoing in numerous countries. This indicates that these disorders may not be rare, but rather have been commonly misidentified and unfortunately for patients worldwide, commonly undiagnosed. Since approximately 2005, every year there are new theories, classifications, and adjustments to the mastocytosis definitions due to escalation of patients presenting with these disorders worldwide.

The current classifications, definitions & diagnostic criteria for Mastocytosis were created by the World Health Organization (WHO)3 after 2004. They have been further updated since then. Unfortunately, they still do not fit all patients presenting with mastocytosis signs and symptoms.6  Specifically, in January, 2010, a group of physicians from the Mayo Clinic wrote a letter to the Editor of Blood Journal, published by the American Society of Hematology, stating the following: "...prognostic relevance of the proposed ISM subclassification has not been validated by primary data." in response to the WHO Indolent Systemic Mastocytosis variant. We have received written permission from Blood Journal to share this letter in full for educational purposes on this website. Click  Pardanani et al - Letter to the Editor7 to view. Competing discussions continue today amongst medical researchers worldwide8 as to the validity of the WHO Mastocytosis disease classification and diagnostic criteria9.

As a result of the limitations of the WHO definitions and diagnostic criteria, physicians created an adjunct Mastocytosis definition & diagnostic criteria which they have named Mast Cell Activation Syndrome (MCAS)4. In addition, there are patients who fit neither the mastocytosis nor MCAS criteria, and they present with Idiopathic Anaphylaxis (IA)5 as their dominant symptom.

The World Health Organization has not yet accepted MCAS or IA as within the definition of Mastocytosis. However, throughout the world, physicians are diagnosing patients with MCAS and/or IA if they do not fit the Mastocytosis criteria but present with the same symptoms. This approach is working, saving patients lives and having some effect on reducing their suffering. All three diagnoses - Mastocytosis, Mast Cell Activation Syndrome (MCAS), Idiopathic Anaphylaxis (IA) - are rare disorders caused by an immune system cell called a mast cell. Our organization represents all those in Canada dealing with these rare disorders.

  1. Canadian Organization for Rare Disorders. http://raredisorders.ca/aboutUs
  2. Be Fair to Rare (Canada). http://befair2rare.com/
  3. McNeill,O., Katelaris,C.:  Disease Summaries - Mastocytosis: Where are we now? World Allergy Organization July 2011. [Open Access]
  4. Molderings,G., Brettner,S., Homann,J., Afrin,L.:  Mast cell activation disease: a concise practical guide for diagnostic workup and therapeutic options. J Hematology & Oncology March 2011. [Open Access]
  5. Abnormal immune cells may cause unprovoked idiopathic anaphylaxis.  News-Medical.net 2007.
  6. Sanchez-Munoz, L; Alvarez-Twose, I; Garcia-Montero, AC; Teodosio C; Jara-Acevedo, M; Pedreira, CE; Matito, A; Morgado, JM; Sanchez, ML; Mollejo, M; Gonzalez-de-Olano, D; Orfao, A; Escribano, L: Evaluation of the WHO criteria for the classification of patients with mastocytosis. Modern Pathology 24, 1157-1168 (September 2011) [Abstract]
  7. Pardanani,A; Lim,K-H; Lasho,T.L; Finke,C.M; McClure,R.F; Li,C-Y; Tefferi,A: WHO subvariants of indolent mastocytosis: clinical details and prognostic evaluation in 159 consecutive adults. Blood Journal 2010 115: 150-151  Pardanani et al - Letter to the Editor
  8. Pardanani,A; Tefferi,A:  Proposal for a revised classification of systemic mastocytosis Blood Journal April 1, 2010 vol. 115 no. 13 2720-2721  [Open Access]
  9. Valent,P; Arock,M; Akin,C; Sperr,W.R; Reiter,A; Sotlar,K; Hartmann,K; George,T.I; Brockow,K; Kluin-Nelemans,H.C; Gotlib,J; Metcalfe,D.D; Horny,H-P: The classification of systemic mastocytosis should include mast cell leukemia (MCL) and systemic mastocytosis with a clonal hematologic non-mast cell lineage disease (SM-AHNMD)  Blood Journal. 2010 August 5; 116(5): 850-851.  [Open Access]

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