There is a condition called Fournier gangrene. It's a rare, fulminant form of necrotizing fasciitis, or "flesh eating" bacterial infection, of the genitals and perineum which most often affects older men with poorly controlled diabetes and chronic alcoholics, although it can afflict anyone. Usually, the nidus (infection focus) is located in the lower gastrointestinal tract, genitourinary system, or skin, in order of frequency.
Most often, Fournier gangrene begins suddenly, with severe pain and swelling in the scrotum or perineum and generalized symptoms of a severe infection, such as fever, chills, lethargy, and altered mental status. There may be redness in the area of the scrotum, perineum, or anus, but the pain extends well beyond the border of the erythema. In about half of cases, the causative bacteria produce air which becomes trapped under the skin. This is called "subcutaneous emphysema" (not to be confused with pulmonary emphysema) and can cause a popping or grating sensation under the skin of the scrotal, perineal, or perianal regions upon palpation, like crushing rice cereal with your fingers. A foul odor is often present, and although the infection originates beneath the skin, within hours, the skin of the genitals and perineum become black and necrotic (dead) as the area is consumed by infection. Without swift treatment, the bacteria will absolutely ravage the penis and perineum, then begin spreading up the abdomen, causing arterial thrombosis which interrupts blood supply to the tissues and causes then to die. There are case reports of the necrosis extending as far as the clavicles!
Treatment of FG includes broad spectrum antibiotics and extensive surgical debridement of dead tissue to stop the progress of the infection. It's unbelievable how much tissue is removed. Some patients require more than one surgical debridement procedure. If the causative infection cannot be controlled with treatment, the patient becomes septic and dies from multiple organ failure. Case mortality is around 40% with treatment.
I'm not going to post photos because they're horrifying, but feel free to Google. This
article provides a good, readable overview of FG and its treatment.