“Wesley,” an apparently healthy newborn boy, develops breathing difficulties and becomes unresponsive around 48 hours after birth. Clinical tests show elevated levels of ammonia and organic acids with corresponding acidemia; genetic tests uncover mutations in the propionic CoA carboxylase gene, a key enzyme in the integration of odd chain fatty acid oxidation and branched chain amino acid catabolism with the TCA cycle. This metabolic integration is derailed by Wesley’s mutated enzyme. Additional negative downstream effects include an inhibited urea cycle. He must be kept on a specific diet and continuously monitored for metabolic crises. A liver transplant is recommended as the best alternative for his long-term survival. Based on a true story, Part I of the case explores Wesley’s metabolic complexities and the relationship between his mutations and the enzyme’s function; Part II (optional) focuses on his liver transplant (see teaching notes for which pages to distribute); and Part III (optional) examines the socioeconomic and psychological challenges facing his caregivers. The case was developed for an undergraduate upper-level biochemistry course as the culminating activity at the end of the semester.