This “clicker case” introduces students to a rare genetic disease in which an enzyme is deficient in a critical metabolic pathway—the first step in aerobic respiration. Based on a real-life situation, the case challenges students to make connections between energy production, enzymes, and metabolic diseases. The case was developed for one-semester, majors’ introductory biology course taken primarily by freshmen and sophomores to fulfill a general education requirement, but could be used in any introductory biology course.  It consists of a PowerPoint presentation (~1MB) shown in class that is punctuated by multiple-choice questions the students answer using personal response systems (aka “clickers”). The case could be adapted for use without these technologies.