What criteria you have to meet to be diagnosed with MCAS depends on which doctor you see – even the experts don’t agree.
| Molderings, Afrin 2011 | Akin, Valent, Metcalfe 2010 | Valent, Akin, Castells, Escribano, Metcalfe et al 2012 | ||||||
| MCAD (umbrella term including both MCAS and SM) diagnosed if both major criteria, or one major criterion and one minor criterion, are present; following bone marrow biopsy, diagnosis is narrowed down to either SM or MCAS | MCAS diagnosed if all criteria are met | MCAS diagnosed if all criteria are met | ||||||
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Major Criteria |
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| Multifocal of disseminated dense infiltrates of mast cells in bone marrow biopsies and/or in sections of other extracutaneous organ(s) (GI tract biopsies; CD117-, tryptase- and CD25- stained) |
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Typical clinical symptoms | ||||||
| Unique constellation of clinical complaints as a result of a pathologically increased mast cell activity (mast cell mediator release symptom) | A decrease in the frequency or severity or resolution of symptoms with antimediator therapy: H1– and H2-histamine receptor inverse agonists, antileukotriene medications (cysteinyl leukotriene receptor blockers or 5-lipoxygenase inhibitor), or mast cell stabilizers (cromolyn sodium) | Increase in serum total tryptase by at least 20% above baseline plus 2 ng/ml during or within 4 h after a symptomatic period | ||||||
| Evidence of an increase in a validated urinary or serum marker of mast cell activation: documentation of an increase of the marker to greater than the patient’s baseline value during a symptomatic period on ≥2 occasions or, if baseline tryptase levels are persistently >15 ng, documentation of an increase of the tryptase level above baseline value on 1 occasion. Total serum tryptase level is recommended as the marker of choice; less specific (also from basophils) are 24-hour urine histamine metabolites or PGD2 or its metabolite 11-β-prostaglandin F2. | Response of clinical symptoms to histamine receptor blockers or MC-targeting agents e.g. cromolyn | |||||||
| Rule out primary and secondary causes of mast cell activation and well-defined clinical idiopathic entities | ||||||||
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Minor Criteria |
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| Mast cells in bone marrow or other extracutaneous organ(s) show an abnormal morphology (>25%) in bone marrow smears or in histologies | ||||||||
| Mast cells in bone marrow express CD2 and/or CD25 | ||||||||
| Detection of genetic changes in mast cells from blood, bone marrow or extracutaneous organs for which an impact on the state of activity of affected mast cells in terms of an increased activity has been proved | ||||||||
Evidence of a pathologically increased release of mast cell mediators by determination of the content of:
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