Background <p>This was an unusual case of invasive pneumococcal disease in an immunocompetent adult without serious underlying medical conditions. Streptococcus pneumoniae bacteraemia was found with multiple distant sites of infection, including polyarticular septic arthritis, osteomyelitis, multi-level spondylodiscitis, and paravertebral, psoas and pelvic abscesses.</p> Case presentation <p>A fit and well 56 year old woman presented with a 10 day history of fevers, rigors, and multiple hot, swollen, tender joints. Septic arthritis was initially thought unlikely, but when blood tests showed marked inflammatory response and the patient was febrile, joint aspiration was performed. Streptococcus pneumoniae was grown from blood cultures and aspirates from multiple joints. MRI confirmed distant sites of infection including left sacroiliac joint osteomyelitis, multi-level spondylodiscitis, and small paravertebral, psoas and pelvic abscesses, which were not amenable to drainage. The patient completed 11 weeks of antibiotic therapy, with IV Amoxicillin followed by IV Ceftriaxone, and made a good recovery with full resolution of joint disease. The patient had obesity but was not in a recognised risk group for invasive pneumococcal disease. No underlying medical conditions were found that would predispose her to such widespread infection.</p> Conclusions <p>Septic arthritis can be polyarticular. Urgent joint aspiration and blood cultures should be undertaken for any patient in whom septic arthritis is considered. Patients with invasive pneumococcal disease should be investigated for predisposing risk factors and should be adequately immunised. This case provides a timely reminder of the virulence of pneumococcus, the severity of invasive pneumococcal disease, and the importance of vaccination.</p>