A 76-year-old woman was admitted to the hospital with shortness of breath. She had tachypnea and was breathing through pursed lips. The patient had a long history of advanced chronic obstructive pulmonary disease (COPD), with a forced expiratory volume in 1 second of 21% of the predicted value. The pulmonary examination showed inspiratory retraction of the intercostal muscles and the suprasternal notch, along with diffuse, polyphonic expiratory wheezing with a prolonged expiratory phase. Symmetric, slanting regions of hyperpigmentation were noted on both thighs, a finding consistent with Dahl's sign, also known as Thinker's sign. Described in 1963 in a patient with severe COPD, Dahl's sign is caused by repeated pressure from the elbows on the epidermis of the thighs in patients spending large amounts of time in the tripod position, resulting in hyperpigmented, hyperkeratotic plaques. Although characteristically found on the thighs, Dahl's sign can also been seen on the elbows of patients who chronically lean forward on a hard surface, essentially creating a callus.