“Pseudo-Geyser Sign” as the First Presentation of Septic Arthritis of the Shoulder

Massive rotator cuff tears can lead to large cysts, extending from the subacromial space through the acromioclavicular joint into a subcutaneous cyst, with a typical “geyser sign” on magnetic resonance imaging (MRI). To our knowledge, no cases of transdeltoid pseudo-cyst as first manifestation of septic arthritis have ever been reported.A 79-year-old female presented to the Emergency Department (ED) with a two-day evolution of a painful tumefaction over her right shoulder. She had been admitted to the ED 16 days before, after being bitten by a dog. Tumefaction drainage revealed a total cell count of 50320 cells/mL. MRI revealed glenohumeral joint cavity’s fluid “decompression” through the deltoid. Septic arthritis was presumed as the cause of the pseudo-cyst, configuring a “pseudo-geyser sign” on MRI.Septic arthritis is an orthopedic emergency, whose early diagnosis, ED referral and treatment are crucial.