This past spring, I started developing a rash on my back. It was macular and itchy and swelled and turned red when I touched it.
“It looks like urticaria pigmentosa except it’s not dark,” one doctor told me. It’s important to note here that my rash pigmentation has been unusual for my entire life. I have, on several occasions, had rashes misdiagnosed because they were “too pink” or “too faint.” I don’t know the reason for this, but it happens. “I’m sure it’s some kind of mast cell issue, your skin is very reactive,” he followed up.
“That is definitely urticaria pigmentosa,” another doctor told me. He touched the spots and they puffed up and got itchy. “See, it has a positive Darier’s sign.” My skin will urticate will very little provocation so I was not convinced. But I figured I was probably bound to have UP eventually, so I wasn’t very concerned.
“It is probably a mast cell rash, but you should get it biopsied just in case,” a third doctor told me. By this point, the rash was all over my back and shoulders. It was itchy, but not all the time. I scheduled an appointment with a dermatologist.
I saw the dermatologist on Thursday. She took one look at it and said, “Oh, that’s not cutaneous mastocytosis. That’s a harmless fungal rash. It’s more common in people who are immunosuppressed. I’ll give you a cream.”
We had a good laugh over the fact that when you have a rare disease, everyone assumes it is the cause of all your symptoms. She told me a funny story about a patient with several rare diseases who had a “mysterious rash” that the residents couldn’t identify. It was tinea versicolor, a very common fungal rash. The residents had assumed it was something exotic and had not considered more mundane options.
Then there was a small fire in the building while I was dressed only in a gown, educating the visiting PCP about systemic mast cell symptoms from skin reactions. I threw my clothes on and ran outside as the fire department arrived. Always lively.
Mast cell disease is hard to manage in part because it can cause so many problems. But just because it can cause all of them doesn’t mean it does.
Mast cell patients are zebras, often many times over. But even zebras mingle with horses once in a while.