Case Presentation: A 68-year-old woman presented to the hospital with dyspnea, lightheadedness, hypoxia and no other systemic symptoms. She had a history of stage IIB small cell neuroendocrine carcinoma of the right lung status post chemoradiotherapy. This was complicated by radiation pneumonitis requiring long-term prednisone. Three days before presentation, she started dapsone 100mg daily for [...]