What is your diagnosis? A solitary purple papule on the arm

A 54-year-old woman with immune thrombocytopenic purpura (ITP) referred to our dermatology department with a three-week-history of a purple-colored lesion on her right arm. The patient was on treatment with oral prednisone at 20 mg/day for ITP and levothyroxine at 25 mg/day for hypothyroidism. No topical treatment was prescribed or used before our consultation. Dermatological examination revealed a 12.5 x 7.5 mm solitary purple papule located on the right upper extremity (Figure 1). Dermatoscopic examination disclosed bluish-red coloration (Figure 2). Surgical excision of the lesion was performed. Histopathological examination of the lesion revealed nodular vascular proliferation in dermis, pronounced congestion and extravagated erythrocytes (Figure 3). What is your diagnosis? What is your diagnosis? A solitary purple papule on the arm