Pembrolizumab-Induced Acral Vasculitis

Immune checkpoint inhibitors (ICIs) have emerged as groundbreaking new therapies for a variety of solid tumors. ICIs stimulate the host immune system to attack cancer cells. However, this nonspecific immune activation can cause autoimmunity across multiple organ systems - this is referred to as an immune-related adverse event. Vasculitis secondary to ICI administration is an extremely rare event seen in <1% of cases. We identified 2 cases of pembrolizumab-induced acral vasculitis at our institution. The first patient, with stage IV adenocarcinoma of the lung, developed antinuclear antibody-positive vasculitis 4 months after initiation of treatment with pembrolizumab. The second patient had stage IV oropharyngeal cancer and presented with acral vasculitis 7 months after starting pembrolizumab. Unfortunately, both cases resulted in dry gangrene and poor outcomes. Here, we discuss the incidence, pathophysiology, clinical features, treatment, and prognosis of patients with ICI-induced vasculitis with the intention of raising awareness about this rare and potentially fatal immune-related adverse event. Early diagnosis and discontinuation of ICIs are critical for improving clinical outcomes in this situation.