Invasive Pyoderma Gangrenosum and Concomitant Methicillin-Sensitive Staphylococcus aureus Septic Arthritis of the Glenohumeral Joint.

A 78-year-old man with a history of multiple cancers presented with severe shoulder pain, elevated inflammatory markers, an ulcerating skin lesion along the anterior shoulder, symptoms concerning for septic arthritis, and a lytic lesion of the humeral head. A negative work-up for malignancy prompted infectious work-up and biopsies, revealing positive methicillin-sensitive Staphylococcus aureus cultures, yet a curious finding of perivascular lymphocytic infiltrates and fibrinoid necrosis from both the dermal vessel wall from a skin biopsy and humeral head bone biopsy, suggestive of pyoderma gangrenosum. This was a previously undocumented presentation of pyoderma gangrenosum invasion into a large joint with concomitant bacterial septic arthritis. [Orthopedics. 2023;46(5):e321-e325.].