This was posted on another mast cell forum.  Dr. Afrin explains in simple terms the difference between Masto and MCAS. Also how everything is categorized under MCAD.  



Mastocytosis in any form -- the rare cutaneous forms such as UP or TMEP, or the even rarer systemic forms -- is a disease of inappropriate mast cell activation combined with inappropriate mast cell proliferation (growth). MCAS, on the other hand, is a disease of inappropriate mast cell activation but with little to no inappropriate mast cell proliferation. Thus, as you can see, it's now evident that *all* mast cell diseases feature inappropriate mast cell activation, but only mastocytosis *also* features inappropriate mast cell proliferation. This is why the new "top-level" term for the whole class of mast cell diseases is "mast cell activation disease" (MCAD). MCAD encompasses both mastocytosis in all its forms as well as MCAS. Current terminology systems in this area say that if you have a diagnosis of UP (or any other form of mastocytosis), then you can't also have a diagnosis of MCAS -- but that's all pretty much an irrelevant semantic point. The bottom line remains two determinations: do you have chronic inappropriate mast cell activation, and do you have chronic inappropriate mast cell growth? (Note that if you have the latter, you virtually certainly also have the former.) Inappropriate activation gets managed with one particular approach (therapies aimed at blocking mediator production, blocking mediator release, and blocking the effects of mediators that have already been released), while inappropriate growth gets treated with a largely different approach (drugs and other techniques that impede mast cell reproduction). The two approaches, of course, are not mutually exclusive, and there are some patients with more aggressive forms of mastocytosis who do in fact get treated simultaneously with both approaches. In many cases of mastocytosis in which there is "less aggressive" inappropriate mast cell growth, though, only therapies targeted at inappropriate mast cell activation are needed.

Overall, the mast cell diseases are highly variable from one patient to the next, thereby requiring that the approach(es) to treatment be as individualized as are the clinical presentations.

-- LBA

It must be a relatively new classification system??? Not that she has seen me as a patient, but from my history and lab results I shared with her, Dr. Castells is thinking I have primary autoimmune urticaria, with a secondary disorder of MCAS. Hmmmm..???

After reading the OP, my understanding is:

Everyone with mast cell diseases has mast cell activation to one degree or another.

Mastocytosis patients also have inappropriate proliferation of mast cells, in addition to inappropriate activation.

It seems that Dr. Afrin would paint all mast cell disorders as MCAD. Under MCAD, every patient will suffer some degree of MCAS.  Another set of patients will have mastocystosis with some degree of MCAS.


IOW, MCAS is there in all MCAD patients.  This is how I read the OP.

Is it different from allergy .. allergic reaction .. Anaphylaxis
With 4 minor criteria and spindle mast cells in bone marrow
I just spent a week with anaphylaxis websites and Thay have never heard of
Mastocytosis clonal mast cell disesse mast cell activation
The awareness campaign has not worked

If the 816v exon 17 mutation was made the major criteria and clusters of mast cells would be minor criteria
Since Tryptase is used as the marker for disesse and progresion the tryptase could be a major as well
But all of theses are found in other disesse
So CD25 would be the major
The we have the few people with murture mast cell infiltration of the bone marrow
Witch course chronic increasing Tryptase in monoclonal mast cell activation
Arfter all this is suited out Thay give you  antihistamines

I need to clarify.  A better way of asking my question would be;

So if it is  a combination of our own specific (genetic) mast cell regulatory elements, and we do not have a positive c-kit, does that make is primary or secondary MCAD?

Hi Lynda. If it's any genetic defect in the mast cells causing the problem then it's a primary MCAD.

A another example is anaphylaxis but arfter servivre clonal anaphylaxis the damage mast cells don't die but keep leaking Tryptase and other chemical s