1) What are the diagnostic criteria?

Go here.

2) What are the symptoms of a systemic mast cell disorder?

Go here. Note that this list is for MCAS and symptomatic systemic mastocytosis. It does not cover symptoms of cutaneous mastocytosis or, of course, asymptomatic cases of indolent systemic mastocytosis.

3) What tests should I ask for?

Go here for initial and mediator testing recommendations and a link to interpreting results.

4) What else might present like a mast cell disorder, or what might suggest my symptoms aren't from a mast cell disorder? 4

Go here, but know that this is a very incomplete list.

5) Is it possible I have aggressive systemic mastocytosis if my tryptase is [insert number here, usually not in the hundreds] or my bone marow biopsy is normal? My spleen...

No.

6) How will I know if I need a bone marrow biopsy?

See interpreting results (of baseline tryptase), but remember that bone marrow biopsies may be important for other conditions, as well, depending on the results of other tests. Your hematologist/oncologist should be able to explain to you why thing 1 and 2 in your results could indicate thing A and B a bone marrow biopsy is necessary to diagnose (for example, blood cancers, some genetic and stem cell diseases, and others). As always, diagnostic value and any possible changes in treatment options should be weighed against any risks this procedure may present to the individual patient. The “what will this change” question is usually relevant. If your tryptase is 200, for example, the results of a bone marrow biopsy together with a C-KIT test could very likely offer you a treatment you can and should try and indicate your (missed) ISM has progressed to smouldering systemic mastocytosis. If your tryptase is 20 and a fourth line therapy is not yet relevant, perhaps checking this every year with your annual physical is more sensible.

7) Someone told me because my tryptase is normal/not that high that I'm okay (I don't need anything). Is that true?

Tryptase is not indicative of disease severity. There are very high risk patients with a tryptase of 2 and patients who live very normal lives with tryptase of 300 (in many cases who also have HATS). Tryptase is, however, somewhat predictive of SM staging for SM patients and HATS.

8) Why doesn't my doctor want to count too many mast cells in my stomach, duodenum, or intestines for the major criteria for systemic mastocytosis diagnosis? (It says “non-cutaneous” organ, and the GI tract is non-cutaneous.)

I know this must be frustrating for you when you are trying to settle on a diagnosis and finally have some laboratory confirmation with “mast cell” highlighted. But this is seen with IBS, too, with Crohn's, with diverticulitis, with other inflammatory conditions, with allergies, with irritating foods, with MCAS, with none of these, and, sometimes, with SM. You also won't find high numbers of mast cells in the GI tracts of every MCAS or SM patient, and since there are so many conditions which are so much more common that can also cause this, it doesn't have as much diagnostic value as we might like other than filling out a picture of irritation or inflammation in the GI tract. Many doctors use this as supporting evidence towards a diagnosis of MCAS.

9) I need a biopsy of some kind (bone marrow, GI, cutaneous...) and have had one before. Do they keep that, so is it possible it can be stained for mast cells, rather than making me repeat the procedure?

Absolutely. Reach out to your doctor. Some have tracked down biopsies nearly from the stone age.

10) I feel like I just need a diagnosis. No one in my area knows MCAS, but some of them know what SM is. What's the risk of going to a doctor dozens of people in a support group promise me will confirm the diagnosis I know I have and put something like SSM or ASM on my chart so the hospital and other doctors will take my reactions seriously? (My tryptase is normal or slightly or moderately elevated, and I either have not had a bone marrow biopsy because my regular doctor knew it wasn't necessary or have had one and it didn't show SM.)

I think we all resent the circumstances which led to this dilemma. I understand why it happens, when it does, and while I disagree, my reasons aren't because I think these patients should be swept under the rug and left to fend for themselves in a broken medical system without adequate support. My reasons are first, that I've met a lot of patients who believe this is what has happened who in fact have some sort of psychosomatic disorder on their chart that they can't see. So when I meet them, no one is taking their symptoms seriously, more so since that “specialist” visit, and 2) For the people who actually have had this erroneously added to their charts by “look at you and maybe run some other tests and diagnose advanced SM” doctors, any ER physician or other with even passing familiarity of these disorders will see that the tryptase rules out this possibility, if there isn't a marrow test that does the same, and they also will not take the patient or anything else written on their charts seriously. So I truly don't believe that having an obviously wrong diagnosis on your chart, even if it is an advanced SM diagnosis medical professionals around you will recognize, is in your best interests...but I'm not omniscient, and I do understand why you're considering this.

If you're a medical provider who's doing this in an attempt to help your patients get the care they need from doofuses, I personally think it would be more helpful to instead include the emergency protocol in their chart with a note explaining why the patient is either diagnosed with or being evaluated for “a serious mast cell disorder” (non-specific) and certain actions and precautions must be taken with respect to their care.

11) I have normal or only slightly elevated tryptase or I've ruled out SM with a bone marrow biopsy. Why is my doctor saying that treatment is needed to confirm a diagnosis of MCAS? Isn't it a little weird to be trying treatment for something if you don't have a confirmed diagnosis?

I see why it might seem that way, but actually not really, considering the number of conditions (not just rare ones) treatment helping is often needed to confirm. (For just one example of an extremely common condition diagnosed with the help of treatment, pulmonary function tests to identify asthma usually use albuterol.) Your doctor's right that it's much less common to be able to support a diagnosis of MCAS without the patient's symptoms improving with appropriate treatment. As much as we would all wish otherwise, mediator testing is still around Flinstones level, and remember, we're trying to catch the fleet-footed messenger rather than the army. Even for patients who do manage to catch evidence of elevated mediator release, if treatment's not helping them, there's likely something else that is at least largely responsible for their symptoms, and we wouldn't know this without their having tried a variety of options that would constitute adequate treatment for their cases.

12) I've done all the mediator tests multiple times and really think that they were handled correctly, and they're still coming up negative. Does this rule out MCAS?

I'm sorry to say this and hope one day that this answer will be different, but no, not at all, and if you do have MCAS, you're actually in excellent company among other MCAS patients who never get laboratory confirmation of elevated mediator release. Mediator testing is currently limited to a tiny fraction of the mediators we know about (hundreds), and these mediators themselves are incredibly short-lived.

13) I've been diagnosed with cutaneous mastocytosis. How will I know if I need a bone marrow biopsy, and how will I know if I need treatment?

If you are an adult and symptoms of cutaneous mastocytosis appeared as an adult, testing baseline serum tryptase will help you decide whether a bone marrow biopsy may be useful for your case. (Cutaneous mastocytosis is a much more common diagnosis in young children and frequently does not lead to a diagnosis of systemic mastocytosis. I recommend talking to your pediatrician and knowledgeable dermatologist about what precautions may be relevant and am sorry CM isn't covered here.) Either way, whether you need treatment will probably depend on whether you have symptoms in other organs/systems. It's certainly possible to have CM with systemic involvement that requires the same treatment options as those for MCAS and SM and CM that leads to a diagnosis of ISM, for example, whether symptomatic or not.

14) Someone told me I need a CT to diagnose this. What's the premedication I need?

First, there is no radiology procedure of any kind that is involved in any element of initially diagnosing any kind of mast cell disorder. Mast cells are not visible in radiology images, and nothing that can be seen in any radiology image is specific to a mast cell disorder. If you need a CT or other radiology procedure to diagnose or rule out some other condition, the usual recommendation is to:

1) delay these procedures outside of emergency or more urgent needs during the initial process of diagnosis, establishing treatment, and identifying your triggers,

2) to premedicate appropriately (see this) and take any other needed precautions, and

3) for most patients, to avoid the use of contrast agents.

Ehler Danlos and other connective tissue disease patients with particular cardiac concerns are often ordered a contrast-free echocardiogram (for which premedication is often also recommended, though in this case no radiation or as significant an electromagnetic field is involved. Vibration may still be a trigger) to rule out aortic aneurysm or other structural abnormalities. Note that the presence or absence of these concerns is not relevant to MCAD diagnosis, and if these provide a reason for, for example, symptoms like an irregular heartbeat, this would be attributed to its structural cause and not count towards an "otherwise unexplained" symptom in a particular organ/system as pertains to MCAS diagnosis.

Thinking about organ enlargement in later forms of SM? Note that these involve palpable organ enlargement (you can feel them), and would only possibly be a consideration well after initial SM diagnosis, once you already meet the criteria for SSM.

15) I was diagnosed with MCAS, but also with one of the things listed under differential diagnoses, and treating that thing (I took some antibiotics for a bad infection, I treated a tick-borne illness, I removed an implant my body was rejecting, I stopped eating my allergens...) completely eliminated my symptoms, so now, since treating the other thing, I'm in remission. I didn't need mast cell treatment at all, or I only needed it until that happened. What should be on my chart?

This is why differential diagnosis is so important before MCAS is confirmed. Certain autoimmune responses, infections, and allergies all activate mast cells in various ways and can produce phenomena that mimic a mast cell disorder...but none of these are MCAS. So if treating some other thing shows you that your apparent MCAS really WAS your lyme, your SIBO, your allergies (For example, if your list of mast cell triggers and allergens is the same, that's how you'd be sure that they're allergens and not mast cell triggers as would arise from a mast cell disorder.), or something else, and treating that other thing eliminated your symptoms, that other thing is almost certainly the correct diagnosis. Remission isn't a term used in this arena for either SM or MCAS, but patients' symptoms often dramatically improve, sometimes (think after years) to the point that they no longer require regular treatment, on mast cell treatment. It's certainly possible to have an asymptomatic case of SM (usually ISM), but MCAS is necessarily symptomatic (MCAS is by nature mast cells acting badly, and thereby creating symptoms, at least without treatment), so while you can certainly get your MCAS OR SM symptoms under control, if something other than mast cell treatment did this and you're now symptom-free after treating that thing, a history of that thing belongs on your chart, and MCAS (or symptomatic SM) does not.