A 73-year-old woman presented with a nail abnormality. She first noticed the condition several months earlier in her toenails, and then it also developed in her fingernails. The patient had no history of similar nail issues. She had previously seen a dermatologist for this condition, and a potassium hydroxide preparation showed no hyphae.

Her medical history was significant for gastroesophageal reflux disease with gastritis diagnosed by esophagogastroduodenoscopy. These symptoms were not well controlled despite treatment with proton pump inhibitors. She also had Graves disease, which was treated with radiofrequency ablation 40 years earlier. The patient was treated with amlodipine for Raynaud disease, but this was discontinued due to hypotension. She was a 90-pack-year smoker but had not smoked for 12 years.

Examination revealed yellowed fingernails with longitudinal striations (Figure 1). The patient's toenails were thickened, brittle, and yellowed with a crumbled appearance (Figure 2).

QUESTION

Based on the patient's history and physical examination, which one of the following is the most likely diagnosis?