Case report: A rare atypical presentation of necrotizing fasciitis with extensive spread secondary to perirectal abscess

Necrotizing fasciitis (NF) is a rare but life-threatening soft tissue infection that spreads rapidly along the fascial planes, causing extensive tissue necrosis and high mortality. Necrotizing fasciitis can be caused by various types of bacteria; the majority of cases are polymicrobial infections. However, necrotizing fasciitis caused by a monomicrobial infection, such as <i>Escherichia coli</i>, is rare. Necrotizing fasciitis can affect any part of the body, but the most common sites are the lower extremities, abdominal wall, and perineum. Necrotizing fasciitis secondary to a perirectal abscess is uncommon and poses a diagnostic and therapeutic challenge. We report a case of a 75-year-old male patient who developed type 3 necrotizing fasciitis of the left gluteal region and left thigh secondary to a perirectal abscess. The patient presented to our hospital with severe pain, swelling, erythema, induration, and fever. He was diagnosed with necrotizing fasciitis based on clinical and radiological findings. He showed gradual improvement and was discharged after 28 days of hospitalization.