RESUMO
BACKGROUND: Fournier's gangrene usually occurs when a specific bacterium intrudes into soft tissue, causing a wound or tumor. We encountered a patient with Fournier's gangrene due to severe myelosuppression after chemotherapy, despite the absence of an initial lesion on the anus and rectum. CASE PRESENTATION: A 54-year-old man with a left testicular cancer recurrence had undergone chemotherapy. He had asymptomatic hepatitis and high hepatitis B virus DNA levels, which were normalized by administering tenofovir alafenamide fumarate. Twelve days after the start of chemotherapy, he complained of severe pain around the anus. The following day, he went into septic shock. Visual inspection showed dark purple skin discoloration on the left side of the anus. Laboratory data revealed severe neutropenia. Computed tomography showed a high density of soft tissue on the left side of the anus and gas bubbles in the left femoral ring. We diagnosed the patient with Fournier's gangrene due to a severe immunosuppressive state resulting from chemotherapy. We emergently removed necrotic tissue to the fullest extent possible. However, because the patient was in severe sepsis status, careful management in the intensive care unit was required for 32 days. After the first emergency operation, we performed several additional excisions. Finally, 391 days after the initial surgery, the patient was discharged from our hospital. The tumor has not recurred, and he is under outpatient observation in the urology department. CONCLUSION: Fournier's gangrene should be considered in patients who are in a severe myelosuppressive state due to chemotherapy, have normal hepatitis B virus DNA levels but high hepatitis B surface antigen after tenofovir administration, complain of severe pain in the perianal area, and have a dark purple skin discoloration around the anus, despite having no initial anorectal lesions.