38. What is the difference between the forms of cutaneous mastocytosis?
Cutaneous mastocytosis is a form of mast cell disease in which way too many mast cells are found only in the skin and not in other organs. Over 80% of patients with mastocytosis have mastocytosis in their skin.
Patients who have systemic mastocytosis have too many mast cells in organs that are not in the skin. However, many of them also have too many mast cells in their skin. These patients are said to have “systemic mastocytosis with mastocytosis in the skin (MIS).” This terminology distinguishes these patients from those who only have too many mast cells in the skin.
There are three categories of cutaneous mastocytosis:
Maculopapular cutaneous mastocytosis (MPCM):
Previously called urticaria pigmentosa (UP). Many patients and providers still use the term UP and the term MPCM is more commonly found in research work.
This is the most common form of cutaneous mastocytosis.
UP causes lesions on the skin, often called “spots” or “masto spots”. In adults, these spots are usually little red/brown lesions. Sometimes a small amount of skin is affected. Other times, a lot of the skin becomes covered in spots.
In adults, UP spots are usually permanent. Some people who need chemo find that the chemo makes some of their UP spots disappear.
In children, UP spots are often larger. The shape and number of spots may change as they get older.
In children, UP spots sometimes resolve over time and disappear.
There is a type of UP called telangiectasia macularis eruptiva perstans (TMEP). This used to be a separate diagnosis from UP but we now know that it is just a kind of UP that looks different from the common red/brown spots.
In TMEP, little blood vessels growth very close to the skin and look like little red or brown spots.
Diffuse cutaneous mastocytosis (DCM):
DCM almost exclusively starts in childhood.
DCM does not cause spots. Instead, it causes overall redness and thickening of skin. It can also cause blistering. The blisters and wounds sometimes bleed.
Solitary cutaneous mastocytoma:
The third form of cutaneous mastocytosis is a little misleading in classification. This form is called solitary cutaneous mastocytoma. This is a benign mast cell tumor that grows on the skin. Mastocytomas can grow elsewhere in the body. When they do, they are not considered a form of cutaneous mastocytosis.
While the term is “solitary cutaneous mastocytoma”, some people do have multiple mastocytomas on their skin.