Topical 5-aminolevulinic acid photodynamic therapy-induced purpura: Involvement of dual antiplatelet therapy (DAPT)

Antiplatelets, widely prescribed for cardiovascular diseases, are associated with an increased risk of bleeding, and careful evaluation is necessary before major surgical procedures. However, current clinical guidelines do not address bleeding risk in the context of noninvasive photodynamic therapy (PDT). We report a case involving a 69-year-old man receiving dual antiplatelet therapy (DAPT) with aspirin and ticagrelor who developed unexpected purpura on both forearms following PDT with 5-aminolevulinic acid for actinic keratoses. A platelet function test (PFT) revealed a prolonged collagen/adenosine diphosphate closure time, consistent with impaired platelet function attributable to DAPT. After modification of the antiplatelet regimen to include aspirin and clopidogrel, platelet function normalized and the purpura resolved. Before the second PDT session, PFT was performed and clopidogrel was withheld for 3 days. The second PDT session was smoothly completed without purpura formation. This report highlights the impact of PDT on platelets and the microcirculation, suggesting that antiplatelet-associated platelet dysfunction may predispose patients to cutaneous bleeding. For enhanced procedural safety and optimal therapeutic outcomes, we recommend comprehensive assessment with PFT before PDT for patients receiving DAPT.