Blue-ink tattoo reaction associated with immune checkpoint inhibitor treatment of metastatic colorectal cancer, a case report

Immune checkpoint inhibitors (ICIs) have revolutionized the field of oncology and transformed the management of many malignancies, especially for patients with metastatic disease. Dermatologic toxicities are among the most common immune-related adverse events (irAEs) of ICIs and can manifest in various ways. We report the case of a 56-year-old male with metastatic colorectal cancer treated with ipilimumab and nivolumab who then developed dermatologic abnormalities confined to the blue-ink regions of his long-standing multicolored tattoos on multiple areas of his body. The patient's reaction resolved after intralesional injection of triamcinolone acetonide. Tattoo reactions associated with ICI treatment are rare, and to our knowledge, there have been no published cases of dermatologic irAEs isolated to blue-pigmented areas of multicolored tattoos. It is of great importance to have awareness of the possibility of this type of reaction and to provide appropriate care for patients undergoing treatment with ICIs.