Dear Editor, Telangiectasia macularis eruptiva perstans (TMEP) is generally considered as a rare telangiectatic subtype of cutaneous mastocytosis without systemic involvement. Typical TMEP presents as multiple discrete red-brown telangiectatic macules which tend to be confluent and persistent. TMEP is usually symmetrically distributed on the trunk and extremities, and do not exhibit Darier's sign or mast cell activation symptoms. 1 Here, we present a rare unilateral TMEP, which differs from previously reported TMEP.A 55-year-old Chinese man presented with an asymptomatic skin rash on the right side of his chest and upper arm that had been present for 7 years. The lesions initially appeared on the flexor aspect of the right upper arm, and had been gradually enlarging and confluent. The patient had no history of herpes zoster and denied pain or other symptoms. Physical examination revealed multiple ill-defined macules and large patches with bruise-like centers and dark-red peripheries, involving the right side of the chest (Fig. 1a) and upper arm (Fig. 1b). Dilated capillary vessels had been noted without significant hyperpigmentation (Fig. 1b). The lesions did not urticate on rubbing. Histopathological analysis showed perivascular mast cell infiltrates (Fig. 1c), which were demonstrated by the expression of CD117 (Fig. 1d) in the upper dermis. Slightly dilated blood vessels had also been noted by the immunohistochemical staining of CD31 (Fig. 1e). Therefore, a diagnosis of TMEP was established, with unilateral distribution. The patient was managed with antihistamines and lost to follow up.Cutaneous mastocytosis is divided into urticaria pigmentosa (UP), diffuse erythrodermic mastocytosis, mastocytoma and TMEP. 2 UP which is the most common form, should be considered in our case. However, the presence of telangiectasias (a) (c) (d) (e) (b) Figure 1. Clinical appearance, histopathological and immunohistochemical analyses of the lesion. (a) Multiple ill-defined macules and large patches with bruise-like centers and dark-red peripheries, involving the right side of the chest and (b) upper arm, and dilated capillary vessels had been noted without significant hyperpigmentation. (c) On histopathological examination, perivascular mast cells (red arrow) infiltrated the upper dermis (hematoxylineosin, original magnification 940). (d) Immunohistochemical analysis revealed CD117-positive cells in the upper dermis (940). (e) Slightly dilated blood vessels had also been noted by the immunohistochemical staining of CD31 (920).