An otherwise healthy 42-yr-old woman comes to the office because she has had gradual formation of grooves on three of the nails on her left hand over the past 3 months. She says the nails are weak and have been splitting and breaking easily during this time. Physical examination shows longitudinal ridging on all three nails with splitting of one of the nails. No other abnormalities are noted. Which of the following dermatologic conditions is most likely associated with this patient’s presentation?