Clostridium septicum Bacteraemia Complicated by Spontaneous Gas-Forming Myositis Revealing a Suspected Caecal Cancer

Clostridium septicum is a Gram-positive, spore-forming anaerobic bacillus that is rarely isolated from blood cultures but is strongly and specifically associated with occult gastrointestinal malignancy, particularly colorectal carcinoma.We describe a 79-year-old woman with a Clinical Frailty Scale score of 6 who presented with vomiting, diarrhoea, fever, rigors, and breathlessness against a background of transitional cell carcinoma treated with nephroureterectomy, type 2 diabetes mellitus, a previous lacunar infarct, and severe ischaemic cardiomyopathy.Blood cultures grew Gram-positive rods identified as Clostridium septicum, and intravenous meropenem was started.Her admission was complicated by unexplained right leg swelling four days into admission and, the following day, right hip pain with reduced range of movement.Magnetic resonance imaging demonstrated a peri-articular collection with gas foci, and computed tomography revealed gas within the right obturator internus and piriformis muscles alongside an irregular, polypoidal caecal lesion suspicious for malignancy, provisionally staged on imaging as T2N0M0.The collection was too small to drain and was managed conservatively with a six-week course of antibiotics, with a sustained fall in inflammatory markers.Given her frailty and multiple comorbidities, the multidisciplinary team elected not to pursue biopsy and to proceed directly to palliative rather than curative management; she was discharged to a nursing home with community palliative follow-up.Clinicians who isolate Clostridium septicum from blood cultures should have a low threshold for musculoskeletal and colonic imaging, since frailty may preclude both histological confirmation and curative treatment even when the underlying association with malignancy is strongly suspected.