Abstract
Acquired methemoglobinemia is a treatable condition that is often clinically subtle and can be missed on routine clinical assessment. We present a 73-year-old male who was evaluated in the emergency department with worsening respiratory symptoms requiring oxygen. He tested COVID-19 positive and had new pulmonary emboli evident on his CT chest. The patient was on dapsone therapy as a treatment for bullous pemphigoid. The discrepancy between his oxygen levels on the pulse oximeter and blood gas was noted and was treated with 3% methylene blue for dapsone-induced methemoglobinemia. The patient received treatment for COVID-19 pneumonia and pulmonary emboli. Our case demonstrates that dapsone-induced methemoglobinemia can present concomitantly with other more common causes of acute hypoxic respiratory failure. It is noteworthy for physicians to maintain a high index of suspicion for oxygen level discrepancy in hypoxic patients and consider the possibility of acquired methemoglobinemia. Hence, earlier detection and treatment of the etiology of tissue hypoxia.