Horizontal Fingernail Lines

Lines on a nail can tell a story about the experiences of the body. This case features a 78-year-old male patient with a past medical history of metastatic prostate cancer, undergoing chemotherapy, who presented to his primary care physician after noticing horizontal white lines on his fingernails. These are most likely to represent Beau’s lines, an arrest in proximal nail matrix proliferation commonly caused by cytotoxic chemotherapy agents. In this case report, we discuss Beau’s lines and other possible etiologies for fingernail lines that may be seen in the primary care setting, and how to identify them.