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Frequency (prevalence) of MCAD

General considerations on frequency

For the prevalence of mast cell activation diseases (MCAD) in the population different numbers are offered around. But before we believe any figures, we have to ask ourselves whether people can be divided clearly enough into “affected” and “unaffected” people. The difficulties:

Unclear diagnostic criteria, high estimated number of unreported cases

In most forms of mast cell activation (MCA), the exact physical cause is not yet known. Clear diagnostic criteria and meaningful diagnostic methods are still lacking. The level of awareness of the disease among the population and doctors is still very low. If someone has ever heard of mastocytosis, he thinks of a very rare skin disease, as was previously taught, and would overlook the much more common forms of MCA. Therefore, the frequency can hardly be recorded at present and there is probably a huge number of unrecognized cases.

Different degrees of severity

With mast cell activation diseases there are different degrees of severity, from only occasionally slightly affected, who do not notice much of it, to very severely affected (incapacity for work or even need of care). The transition between "affected" and "not affected" is fluid.

External factors (environ­mental mast cell activation)

The degree of concern also depends on the currently prevailing environ­mental factors or civili­zational "achievements" (eating habits, stress, medication, environ­mental pollutants, etc.). Basically, the mast cells of every human being can be activated if the stimulus is strong enough (e.g. tear gas). This is just a question of dose. However, a "healthy" person only feels this in rare extreme combinations (e.g. a lot of alcohol, mast cell-activating foods and perhaps an additional medication).

Some are only temporarily affected

Only a few have been affected since birth. Some people develop this mostly acquired disease at some point in their lives, others are only temporarily affected, e.g. during infections, drug or alcohol abuse, drug use, intake of environmental toxins, certain weather conditions, menstrual cycles, etc. Episodic courses without recognizable external triggers are also observed.

Where should one draw the line between the affected and the unaffected part of the population?

Nevertheless, here are some examples of sources with information on prevalence:

Bibliographical references on the frequency of mast cell activation diseases:

• “Bis vor kurzem war es weitver­breitete Ansicht, dass die MCAD zu den seltenen Erkrankungen gehört. Dies trifft aller­dings nur für zwei Unter­klassen zu: für die systemische Masto­zytose und die Mastzell­leukämie, deren Präva­lenzen mit 1:364 000 bzw. noch mindestens 2 Grössen­ordnungen geringer berechnet wurden [Haenisch et al. 2012]. Dagegen betrug die Prävalenz der MCAD in der deutschen Bevölkerung in einer aktuellen ersten Studie bis zu 17 % [Molderings et al. 2013]. Diese hohe Prävalenz muss in weiteren grossen epidemio­logischen Unter­suchungen noch bestätigt werden. Ueber­raschend ist diese hohe Prävalenz jedoch nicht, denn sie ist vermutlich Ausdruck des häufigen Auftretens des Mastzell­aktivierungs­syndroms, das ursächlich verschie­denen häufig auftre­tenden klinischen Erkran­kungs­bildern wie bestimmten Formen der Fibro­myalgie [...] und Untergruppen des Reizdarm­syndroms [...] zugrunde liegen kann.” [Molderings et al. 2014]
  
  English translation: Until recently, it was widely believed that MCAD is a rare disease. However, this only applies to two subclasses: systemic mastocytosis and mast cell leukemia, whose prevalences were calculated to be 1:364 000 or at least 2 orders of magnitude lower [Haenisch et al. 2012]. In contrast, the prevalence of MCAD in the German population in a recent first study was up to 17 % [Molderings et al. 2013]. This high prevalence has yet to be confirmed in further large epidemiological studies. However, this high prevalence is not surprising because it is probably an expression of the frequent occurrence of mast cell activation syndrome, which can be the cause of various frequently occurring clinical diseases such as certain forms of fibromyalgia [...] and subgroups of irritable bowel syndrome [...].
  
• “Increasing estimates of prevalence: 1 - 17% of the general first-world population?” [Afrin 2014]
  
• “The prevalence of MCAD suspected by symptom self-report in first-degree relatives of patients with MCAD amounted to approximately 46%, compared to prevalence in the general German population of about 17% (p<0.0001). [...] The immuno­histo­chemically different subtypes of MCAD (i.e. mast cell activation syndrome and systemic mastocytosis) should be more accurately regarded as varying presen­tations of a common generic root process of mast cell dysfunction, than as distinct diseases.” [Molderings et al. 2013]
  
• “Few data are available concerning the prevalence of systemic MCAD. SM and MCL are rare disorders. For SM, data from the French masto­cytosis network AFIRMM, the Spanish mastocytosis network REMA, the Italian Mastocytosis Registry, and the German Competence Network on Mastocytosis (own unpublished results; personal communi­cations), suggest a prevalence of at least 1 in 364,000 in Europeans. However, given that these data represent only a proportion of all cases, the true prevalence will be higher. Data from a clinical population suggest that the prevalence of MCL is two orders of magnitude lower than that of SM. In contrast, MCAS seems to be a more common disorder. Evidence has been presented that MCAS may be an underlying cause of various clinical presen­tations, e.g. in subsets of patients with fibromyalgia and irritable bowel syndrome. Hence, the prevalence of MCAS is likely to lie within the single-digit percentage range.” [Haenisch et al. 2012]
  
• “[...] we can assume an average frequency for histamine-induced intolerance symptoms within the general population of 5 to 8%, whereby not all of those affected seek doctor's advice.” [Raithel 2012]
  

Here are some more numbers about incompatibilities in general:

“More than 20% of the population in industrialized countries suffer from food intolerance or food allergy. [...] The majority of cases of food intolerance (15% to 20%) are due to non-immunological causes. These causes range from pseudoallergic reactions to enzymopathies, chronic infections, and psychosomatic reactions that are associated with food intolerance. The prevalence of true food allergy, i.e., immunologically mediated intolerance reactions, is only 2% to 5%.” [Zopf 2009]

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