ABSTRACT
A 58-year-old man known to dermatology services, established on guselkumab for psoriasis and methotrexate for psoriatic arthritis, attended with an acute onset purpuric rash distributed over both his lower limbs, one day after his third dose of SARS-CoV-2 Pfizer-BioNTech vaccine (booster). He had received his initial vaccinations 6 months prior with no reported reactions. He denied any previous SARS-CoV-2 infection or recent symptoms suggestive of COVID-19. There had been no new recent medications and no systemic symptoms were reported. Examination revealed a nonblanching, palpable, purpuric rash distributed over both lower limbs, clinically in keeping with cutaneous vasculitis. Baseline observations were satisfactory including blood pressure and temperature. Bedside investigations included a urinalysis which revealed no proteinuria or haematuria. Punch biopsies were taken and were consistent with a leucocytoclastic vasculitis (LCV). He was managed symptomatically with potent topical steroids with good clinical response. LCV is classified as a cutaneous, small vessel vasculitis, exclusively characterized by deposition of immune complexes in the dermal capillaries and venules (Baigrie D, Bansal P, Goyal A, Crane JS. Leukocytoclastic vasculitis. In: StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing, 2021). LCV following both first and second SARS-CoV-2 vaccinations has been documented in recent literature with a few reports following a third booster dose, and in particular within an immunocompromised population. This particular case has raised questions regarding delayed immune response following SARS-CoV-2 vaccine in this subgroup. The pathophysiology of SARS-CoV-2 vaccine-induced LCV has not been extensively researched;however, it is felt to be caused by offtarget immune activation after the vaccination (Dicks AB, Gray BH. Images in vascular medicine: leukocytoclastic vasculitis after COVID-19 vaccine booster. Vasc Med 2022;27: 100-1).