We present a case of necrotizing fasciitis initially presenting as septic hypoxic pneumonia, and discuss imaging modalities and diagnostic evaluation. Necrotizing soft tissue infection (NSTI) is a rapidly progressive surgical emergency with a mortality rate of 30%. In approximately 80% of cases, it is introduced through a break in the skin. It can also occur after any invasive procedure or surgery. It is most commonly associated with skin flora including staph and strep, though polymicrobial infections are most common. It usually presents with signs of systemic infection, including fever, chills, sepsis, altered mental status - and signs of cutaneous involvement on physical exam, including erythema / discoloration, sloughing and blistering, and pain out of proportion to exam, and crepitus. The crepitus or findings of subcutaneous emphysema on imaging are due to gas-producing bacteria from polymicrobial infection. Blood work can help support the diagnosis of a systemic infection, including things like elevated white blood cell count, elevated lactic acidosis, and other systemic inflammatory markers. Imaging can show signs of free air, particularly on x-ray, ultrasound, or CT. Poor prognosis is associated with comorbidities, advanced age, immunocompromised state, shock. The definitive treatment is early surgical debridement of the necrosed tissue, and antibiotics. Surgical exploration usually confirms the diagnosis, with foul gray fluid expressed, necrosis and gangrene of underlying tissues and muscles, and friability of muscles on dissection. Hypoxia and tachypnea can have a broad differential diagnosis, including but not limited to reactive airway disease, heart failure, pneumonia, pulmonary emboli. In the setting of fever and cough, a working clinical diagnosis of pneumonia can be considered
