Eyelash trichomegaly complicating pembrolizumab for colorectal cancer.

Introduction: Pembrolizumab is an immune checkpoint inhibitor widely administered for the treatment of various malignancies. Despite its effectiveness, its distinctive mechanism of action may lead to immune-related adverse events, most frequently affecting cutaneous tissues. Hair-related adverse events, although uncommon, include conditions such as alopecia areata and alterations in hair texture or type.

Case report: A 63-year-old male patient presented with eyelash trichomegaly following two cycles of pembrolizumab infusion.

Treatment and outcome: The patient experienced discomfort due to the eyelash trichomegaly, prompting him to consider discontinuing the treatment. However, the patient's neoplastic disease demonstrated a complete radiologic response, which encouraged him to continue the therapy.

Discussion: This case illustrates a unique documentation of pembrolizumab-induced eyelash trichomegaly. While immune checkpoint inhibitors like pembrolizumab are known to cause hair-related adverse events, reports of eyelash trichomegaly remain rare. This case emphasizes the necessity for clinicians to remain vigilant about such uncommon side effects to ensure comprehensive patient management.