I have always struggled with the diagnosis of telangiectasia macularis eruptive perstans (TMEP). Aside from taking the first 6 months of my residency to remember how to say it, I have never been confident of securing the diagnosis. It would always enter the differential diagnosis when telangiectasias were observed, especially on the trunk. Classically the Darier sign is negative in TMEP. If a lesion is biopsied, how many perivascular mast cells are necessary to define the entity? Even if you are confident of the diagnosis, what is the likelihood of systemic involvement?
Severino et al, surveying 243 patients with cutaneous mastocytosis, classified 34 (14%) as TMEP. Sixteen of the 34 (47%) had systemic mastocytosis, with 3 (9%) having “aggressive” mastocytosis (manifested by bone fractures and/or gastrointestinal injury resulting in malabsorption and weight loss). Their patients were diagnosed by skin biopsies for routine microscopy, immunohistochemical stains using anti-CD 117, and detection of a KIT point mutation at codon 816.
The authors noted that the low number of mast cells in dermal tissue, the low frequency of KIT point mutations, and the low serum tryptase levels in patients with TMEP suggest a lower mast cell burden than in other forms of mastocytosis. What is hard to grasp, therefore, is the high frequency of systemic manifestations in TMEP. What is especially disconcerting is that the tryptase levels were normal in many TMEP patients with systemic symptoms, with only 9 (26.5%) having levels > 20 mg/L (1).
I have been relying on the serum tryptase level of > 20mg/L as the time to consider referring patients with mastocytosis for systemic evaluation by a hematologist. Perhaps I have been relying too much on a number, and not enough on a review of systems inquiring about fatigue, diarrhea, flushing, dyspnea, etc. While the authors acknowledge that their study may be subject to referral bias, it is hard to argue with their conclusion that more work is needed to better define the diagnostic criteria of TMEP.
In a retrospective review of 299 cases of mastocytosis using the NIH Biomedical Translational Research Information System, Williams et al identified 24 cases of TMEP. The majority of these patients had systemic manifestations, including 9 with anaphylaxis and 4 with syncope. The Darier sign was positive in 40% of their TMEP patients and the median serum tryptase level was 24.2 ng/ml. Twenty-one patients underwent bone marrow biopsy for evaluation of possible systemic mastocytosis. Sixteen patients (67%) met the WHO diagnostic criteria for indolent systemic mastocytosis, 7 (29%) had mastocytosis limited to the skin (MIS, all UP), and 1 patient did not meet criteria for MIS or systemic disease (4%).
The authors conclude by stating “the diagnosis of TMEP appears to be over-used, has little clinical utility and is confusing to physicians and patients. Highly vascularized UP more accurately describes these pigmented macular lesions that localize with observable telangiectasia. We suggest that in the majority of instances where the diagnosis of TMEP is used, the lesions are more accurately described as UP” (2).
Personally, I do not think that the term TMEP will be expunged from the dermatologic lexicon. Future generations will be proud to make the diagnosis. What will be different, however, is that more consistent diagnostic criteria will be forthcoming, and there will be an appreciation that TMEP may imply far greater systemic involvement that previously perceived.
- Severino M, et al. Telangiectasia macularis eruptive perstans (TMEP): A form of cutaneous mastocytosis with potential systemic involvement. J Am Acad Dermatol 2016; 74: 885-91.
- Williams KW, et al. Telangiectasia macularis eruptive perstans or highly vascularized urticaria pigmentosa? J Allergy Clin Immunol Pract 2014; 2: 813-5.