<prompt> What is the most likely cause of this presentation?ChemotherapyHyperthyroidismNephrotic syndromePsoriasis  <response>: Answer A. ChemotherapyThese multiple white lines on the fingernails, known as Beaus lines, correspond with chemotherapy cycles in this patient with gastric cancer. Cytotoxic chemotherapeutic agents can induce the temporary arrest of proliferative function of the nail matrix. 