P098 FROM OLD BUMP TO BONE INFECTION: A CASE OF BRODIE’S ABSCESS IN A CROHN’S PATIENT

Abstract Introduction Brodie’s abscess is an uncommon variant of subacute osteomyelitis leading to a contained infectious focus within a bone. It classically occurs in young people with a history of trauma to the affected bone. We present a case of a Brodie’s abscess in a 52-year-old Crohn’s patient on dual immunosuppressive therapy. Case Description A 52 year old man with Crohn’s disease managed with adalimumab and methotrexate presented to an orthopedist with worsening left hip and thigh pain and fevers over the week prior. He reported a remote sports-related injury to the same region with mild pain intermittently over the subsequent years. MRI of the left pelvis showed an enhancing lesion of the anterior superior iliac spine with cortical erosion. He was admitted and started on broad spectrum antibiotics, and his immunosuppressive agents were held. CT-guided biopsy of the lesion returned as abscess, and culture of the lesion grew methicillin-sensitive staphylococcus aureus. The abscess was debrided in the OR and he completed a 6-week course of culture-guided antibiotic therapy. Discussion To our knowledge this is the first reported case of Brodie’s abscess associated with Crohn’s disease and dual immunosuppressive therapy. Opportunistic pathogens are most often associated with anti-TNFα therapy, though there is also evidence other bacterial infections are more frequent in these patients, particularly salmonellosis, listeriosis, and pneumococcal disease. Patients on anti-TNFα therapy appear to be at highest risk for serious infections in the first six months after initiation, but it is unclear if there is a persistent or cumulative risk with long-term therapy. The underlying mechanism of immunosuppression in anti-TNFα therapy is thought to be multifactorial, impacting both innate and adaptive immunity. Data suggests increased risk of infection in rheumatoid arthritis patients taking methotrexate. Only observational data exists regarding infection risk in Crohn’s patients on methotrexate, but it is reasonable to infer that it may have played a role in our patient’s presentation. Bone trauma seems to be associated with the development of Brodie’s abscess, and our patient reported a long history of chronic left hip and thigh pain due to a remote sports-related injury to that region. The source of his infection was most likely transient bacteremia, which seeded this nidus in his anterior superior iliac spine. While causation cannot be determined, this intere