Telangiectasia macularis eruptiva perstans (TMEP) is a rare form of cutaneous mastocytosis (CM). Although TMEP has been traditionally thought to be restricted to the skin, a recent retrospective multicentric study established a diagnosis with systemic involvement of mastocytosis in 47% patients affected by TMEP and aggressive systemic mastocytosis in 9%. To evaluate systemic involvement in patients affected by TMEP. We conducted a retrospective monocentric study among patients affected by TMEP visited in our dermatology clinic. Data regarding gender, age at diagnosis, duration of the disease before diagnosis, topography, clinical features, presence of extra-cutaneous symptoms, serum tryptase levels, and histopathological and bone marrow biopsy features were analysed. Among 119 patients classified with mastocytosis, eight patients (six males, two females) with TMEP and one female patient affected by mastocytosis in the skin, a TMEP variant, were retrospectively studied. The mean diagnostic delay was two years (range: 8-26 months). In two patients (25%), bone marrow involvement was identified and osteoporosis and hepatosplenomegaly were also found. The two patients with systemic involvement exhibited a statistically significant increase in serum tryptase levels (p < 0.05). The detection of KIT gene mutation in skin specimens revealed a somatic mutation, KITD816 V, only in these two patients. TMEP is a rare form of CM, often neglected. A correct and early diagnosis of TMEP is important to rule out systemic involvement of the disease. Detection of serum tryptase levels may be a useful, rapid, and non-invasive marker of systemic involvement.