Cutaneous mastocytosis and systemic symptoms

I want to clear up some confusion about systemic symptoms and systemic disease as pertains to mastocytosis.

Urticaria pigmentosa (UP) and telangiectasia macularis eruptiva perstans (TMEP) are forms of cutaneous mastocytosis (CM.) These manifestations are caused by dense infiltrates of mast cells in the skin.  Skin is the organ most likely to be infiltrated by mast cells. 

Patients who have UP or TMEP WHO DO NOT HAVE SYSTEMIC MASTOCYTOSIS can still have symptoms that pertain to organs other than the skin.  This means that these UP and TMEP patients can have flushing, blisters, shortness of breath, low blood pressure, nausea, vomiting, diarrhea, and other mast cell symptoms.  The mast cell mediators released in the skin can move through the tissue and cause other mast cells to degranulate, causing systemic symptoms.  The frequency of systemic symptoms is proportional to the amount of skin affected by the UP or TMEP rash.  This is because the more rash is present, the more mast cells are there to release mediators. 

The fact that you have systemic symptoms (by which I mean anything that is not related to skin) does NOT mean that you have systemic mastocytosis (SM.) There is a lot of confusion about systemic symptoms vs systemic disease (SM.)  YOU DO NOT NEED TO HAVE A DIAGNOSIS OF SM TO HAVE SYSTEMIC SYMPTOMS WITH CM.  SM implies infiltration of an organ that is not the skin.  It has its own diagnostic criteria that I have gone over before.

However, if you have CM and you are an adult, you might develop SM.  Dr. Escribano stated in the late 90’s that as many as 80% of patients with long standing CM had “positive bone marrow biopsies.”  However, this was before the 2008 WHO criteria (obviously) and I have not been able to find out exactly what he considered “positive.”  I will keep you guys posted on that.  Chronic elevation of tryptase, expression of CD25 by the skin mast cells or presence of the D816V CKIT mutation are all factors that can indicate a CM case that will progress to SM.  Suffice it to say, I know a fair amount of people who have UP and went on to be diagnosed with SM.  It’s not that big of a jump. 

If you have UP or TMEP and then go on to develop SM, you then have a diagnosis of SM with skin involvement.  SM supercedes the CM diagnosis. 

I have recently seen people describe their disease as UP with MCAS or something like that.  This is not possible.  MCAS is a diagnosis of exclusion.  It is the diagnosis you get when you have mast cell disease and meet the criteria for none of the other mast cell diseases.  I think this sometimes happens because doctors are not aware that you have systemic symptoms (even anaphylaxis) with CM.  Systemic symptoms in CM patients should be treated the same way as they are in MCAS or SM patients. 

I have also recently seen people say they have SM and MCAS.  I am here to tell you that you can’t have both.  Some people with SM have lots of systemic symptoms and some don’t.  MCAS does not refer to a state of reactivity or severe symptoms.  It refers to mast cell dysfunction in the absence of an identifiable mast cell disease with known diagnostic criteria.