IL: interleukin RAS: recurrent aphthous stomatitis OBSERVATION Recurrent aphthous stomatitis (RAS) is a common cause of recurrent oral ulcers, which often leads to significant impairment of a patient’s quality of life. The underlying pathogenic mechanism remains unclear, and no treatment modality is uniformly effective. In this report, we describe the use of apremilast, an oral phosphodiesteras...