Telangiectasia macularis eruptiva perstans (TMEP) is a rare type of mastocytosis that presents as multiple asymptomatic, flat, reddish-brown lesions on the skin. This skin disorder is caused by an increased number of mast cells entering the skin. Mast cells are made in the bone marrow and are part of the body’s immune system. These cells, once activated, release a variety of proteins and chemicals that create allergic reactions and attract other cell types to fight off infections. Mastocytosis can either be cutaneous (affecting only the skin) or systemic (affecting various parts of the body), with cutaneous mastocytosis being more common. In addition, cutaneous mastocytosis is more common in children. However, TMEP is more often seen in young adults, though it has been seen in children.

TMEP is characterized by persistent, reddish-brown macules that range in size from 2 to 6 millimeters in diameter with irregular borders. Telangiectasias, which are dilated blood vessels on the skin surface (also called spider veins), may or may not be present. Darier’s sign, a reaction to skin being rubbed/agitated resulting in redness and swelling, is usually absent, unlike other types of mastocytosis. TMEP usually significantly affects the trunk and the arms or legs, covering both sides of the body in a symmetric pattern. However, there have been a very small number of reports of TMEP affecting one side of the body. Though it typically just affects the skin, TMEP has an increased chance of causing systemic symptoms including flushing, a racing heart, difficulty breathing, decreased blood pressure, heartburn, and diarrhea, but these are still uncommon. Of note, the few cases that have only affected one side of the body did not have any systemic symptoms.

To diagnose TMEP, a biopsy will show an increased number of mast cells around blood vessels. In addition to the biopsy, the clinical appearance of the lesions, the absence of Darier’s sign, and age of onset can all point to the diagnosis.

TMEP is a benign condition, but special care should be taken in patients who have significant systemic symptoms to prevent complications.

Mainstays of treatment includes antihistamines, which prevent the activation of the mast cells, as well as treatment to reduce the appearance of the rash with pulsed dye laser. As many patients are asymptomatic, no treatment is needed and patients may opt to cover up the lesion cosmetically with makeup.

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