Our patient exhibited transverse leukonychia of the fingernails, which is thought to result from abnormal keratinization of the nail plate due to systemic disorders that induce a temporary dysfunction of nail growth.9 Fernandez-Nieto et al7 reported transverse leukonychia in a patient with COVID-19 that was hypothesized to be due to a transitory nail matrix injury.
Beau lines and onychomadesis, which represent nail matrix arrest, commonly are seen with systemic drug treatments such as chemotherapy and in infectious diseases that precipitate systemic illness, such as hand, foot, and mouth disease. Although histologic examination was not performed in our patient due to cosmetic concerns, we believe that inflammation induced by the vaccine response also can trigger nail abnormalities such as transverse leukonychia and Beau lines. Both SARS-CoV-2 infections and the COVID-19 messenger RNA vaccines can induce systemic inflammation largely due a TH1-dominant response, and they also can trigger other inflammatory conditions. Reports of lichen planus and psoriasis triggered by vaccination—the hepatitis B vaccine,10 influenza vaccine,11 and even COVID-19 vaccines1,12—have been reported. Beau lines have been observed to spontaneously resolve in a self-limiting manner in asymptomatic patients with COVID-19.
Interestingly, our patient only showed 2 nails with Beau lines. We hypothesize that the immune response triggered by vaccination was more subdued than that caused by SARS-CoV-2 infection. Additionally, our patient was already being treated with immunosuppressants, which may have been associated with a reduced immune response despite being withheld right before vaccination. One may debate whether the nail abnormalities observed in our patient constituted an isolated finding from COVID-19 vaccination or were caused by reactivation of rheumatoid arthritis. We favor the former, as the rheumatoid arthritis remained stable before and after COVID-19 vaccination. Laboratory evaluations and physical examination revealed no evidence of flares, and our patient was otherwise healthy. Although the splinter hemorrhages also improved, it is difficult to comment as to whether they were caused by the vaccine or had existed prior to vaccination. However, we believe the melanonychia observed in the nails was unrelated to the vaccine and was likely a chronic manifestation due to long-term hydroxychloroquine and/or methotrexate use.
Given accelerated global vaccination efforts to control the COVID-19 pandemic, more cases of adverse nail manifestations associated with COVID-19 vaccines are expected. Dermatologists should be aware of and use the reported nail findings to educate patients and reassure them that ungual abnormalities are potential adverse effects of COVID-19 vaccines, but they should not discourage vaccination because they usually are temporary and self-resolving.