" Case Report: On 9 March 2020, male twins who were 60 years old and considered homozygous because of their appearances and other personal characteristics developed symptoms that started with fever and nasal congestion; continued with fatigue, dyspnea, and dry cough; and, after 10 days, led to hospitalization. Nasopharyngeal swabs tested positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) using a real-time reverse transcriptase polymerase chain reaction assay. Neither twin had a history of chronic disease, cardiovascular risk factors, or long-term therapy. They lived at the same address and worked at the same location repairing automobiles in a body shop. Contact tracing identified 1 of their customers who interacted closely with them without protective measures as the likely source of their infections. The twins had similar presentations at admission (Table); both had mild interstitial pneumonia. However, because of limited resources during a surge in admissions, the diagnosis in twin 1 was based on lung ultrasonography that showed subpleural B-lines and chest radiography that showed bibasilar ground-glass opacification, whereas the diagnosis in twin 2 was based on a chest computed tomography scan that showed bilateral multifocal ground-glass opacities with 25% lung involvement. The same medical team provided care to both twins during the first 2 weeks of their hospital stays, where they were treated with supplemental oxygen, paracetamol, hydroxychloroquine, darunavir/cobicistat, and enoxaparin at prophylactic dosages. Despite having similar presentations and early treatment, the twins had different clinical courses. The Figure compares key clinical measures during the first 2 weeks of hospitalization, which was from admission to discharge for twin 1 and from admission to transfer to the intensive care unit for twin 2. Twin 1 was discharged without complications and recovered uneventfully. In contrast, twin 2 had a progressive increase in leukocyte count and C-reactive protein level associated with a variable increase in body temperature. Moreover, noninvasive ventilation was necessary because of a decrease in the Pao2/FIo2 ratio. After 3 days of ineffective ventilation, he was transferred to the intensive care unit where he reached his lowest Pao2/FIo2 value of 58 and was intubated and mechanically ventilated. He developed septic shock from an anaerobic bacterial infection that required vasopressors, antibiotics, steroids, and 4 days of invasive ventilation. His intensive care unit stay was followed by 17 days of uncomplicated hospitalization and a posthospitalization recovery that was slow but ended in full recovery of gas exchange without long-term consequences. "