Pubic symphysis osteomyelitis presenting as groin pain in a patient with rheumatoid arthritis: a case report

Osteomyelitis of the pubic symphysis is a rare entity, affecting less than 1% of all osteomyelitis cases. It most frequently occurs in individuals with predisposing conditions, including states of immunosuppression, a history of pelvic or urogenital surgery, and intravenous drug use. In patients with rheumatoid arthritis (RA), the diagnosis can be substantially delayed because clinical manifestations may mimic or overlap with those of inflammatory joint disease. We describe a case of presumed culture-negative osteomyelitis of the pubic symphysis in a patient with RA, emphasizing the diagnostic challenges and therapeutic considerations in this complex clinical setting.

A woman in her late 60s with long-standing seropositive RA, managed with methotrexate and prednisolone, and with comorbid type 2 diabetes mellitus, hypertension, and osteoporosis, presented with a two‑month history of progressively worsening right groin pain refractory to analgesic therapy, leading to significant functional limitation and gait impairment. On admission, she was afebrile with hemodynamically stable vital signs. Physical examination revealed suprapubic tenderness and a reduced range of motion of the right hip. Laboratory investigations showed leukocytosis (14.2 × 10⁹/L, 91% neutrophils), markedly elevated C‑reactive protein (149 mg/L), and an increased erythrocyte sedimentation rate (133 mm/h). Blood cultures remained sterile, whereas urine culture grew methicillin‑sensitive Staphylococcus aureus (MSSA). Serological testing for brucellosis and a tuberculin skin test were both negative. Contrast‑enhanced computed tomography (CT) of the pelvis demonstrated an abscess involving the pubic symphysis associated with reactive osteitis. Culture of aspirated abscess material was sterile, and histopathological examination of the biopsy specimen showed nonspecific inflammatory changes without granulomatous inflammation. Empirical antimicrobial therapy with intravenous cefazolin and ciprofloxacin was administered for 30 days, followed by oral ciprofloxacin and doxycycline for an additional two months. The patient achieved complete clinical and laboratory resolution without the need for surgical intervention. Follow‑up CT imaging confirmed resolution of the abscess, with residual diastasis of the pubic symphysis.

Pubic symphysis osteomyelitis should be included in the differential diagnosis of atypical pelvic pain in immunosuppressed patients with RA. Ongoing immunosuppressive therapy may obscure or attenuate systemic manifestations of infection, thereby contributing to delayed diagnosis. Early utilization of cross-sectional imaging modalities and the administration of prolonged, targeted antimicrobial therapy are critical to achieving favourable clinical outcomes.