IntroductionInfectious extensor tenosynovitis is a rare infection spreading along the extensor tendons of the extremities. It presents a diagnostic challenge in the emergency department (ED) given the nonspecific signs and symptoms, as opposed to the more common flexor tenosynovitis that is diagnosed by the classic Kanavel signs on physical exam.Case ReportHere we present a case of bilateral extensor tenosynovitis in a 52-year-old female denying past medical history who presented to the ED with two days of bilateral dorsal hand swelling and pain. She denied any risk factors such as direct trauma to the hands or intravenous drug use. The rare diagnosis was suspected in the ED due to a very high complement reactive protein level and a concerning point-of-care ultrasound. Extensor tenosynovitis was ultimately confirmed on computed tomography and by operative irrigation and drainage of the tendon sheaths.ConclusionThis case demonstrates the importance of keeping extensor tenosynovitis on the differential when seeing a patient with dorsal extremity edema and pain, even if the findings occur bilaterally.