Introduction and aim. Gas gangrene is usually related to a trauma and can involve different districts of the body. It is a life-threatening condition, and its consequences lead to functional and aesthetical deficit. Atraumatic gas gangrene is a rare event, sometimes related to a Clostridium septicum (C. septicum) bacteremia. Aim of this article is to discuss existing literature about relation between colon adenocarcinoma and Clostridia infections, integrating with a case-report. Patients and methods. A 54-year-old obese female patient developed an atraumatic gas gangrene of the posterior trunk, started from a C. septicum bacteremia. Gas gangrene involved skin, soft tissues and muscles of the back. A multidisciplinary clinical and surgical management involved anesthesiologists, general and plastic surgeons. During hospitalization, an occult colon adenocarcinoma was diagnosed and recognized as the bacteremia trigger, and it was successfully addressed. The gangrene was properly treated with seriate surgical debridement and final soft tissue coverage. After a long hospital stay, the patient was discharged in stable clinical conditions. Results and conclusions. C. septicum gas gangrene remains one of the most fearful infections. An early diagnosis and a prompt antibiotic and surgical treatment, with life supportive care, are mandatory to avoid the necrotizing fasciitis spreading and the death of the patient. However, due to the rarity and variability of this condition, there is no standardized protocol for its treatment. Since a strong relation between C. septicum infection and colon malignancy is reported in literature, in cases of C. septicum bacteremia it should be mandatory to investigate gastrointestinal tract to exclude colon malignancy.