The most serious form is necrotizing fasciitis, a progressive necrotic infection of the deep subcutaneous fascia and fat, which begins with trauma (inconspicuous trauma) or surgery with localized redness, swelling, heat, and pain that quickly extends outward. 24-48 hours later, the lesion changes color from red to purple, then blue to form blisters and blisters containing yellow fluid. On the 4th to 5th day of illness, the purple area began to necrotize, and on the 7th to 10th day, the border was clear and the necrotic skin fell off, revealing extensive necrotic tissue under the skin. Patients with high fever and debilitated response are very susceptible to bacteremia and sepsis, and in fact TSLS patients are mostly associated with severe soft tissue infections. Diagnostic criteria for progressive necrotic infection of deep subcutaneous fascia: 1. Extensive necrosis of superficial subcutaneous fascia with extensive submerged pits spreading into surrounding tissues. 2, Moderate to severe signs of systemic toxicity with altered mental status. 3, No muscle involvement. 4.Wound and blood cultures did not reveal Clostridium perfringens. 5.No significant vascular obstruction. 6.The debridement histopathological examination revealed extensive leukocyte infiltration, focal necrosis of fascia and adjacent tissues and microvascular embolism. Bacteriological examination is important for diagnosis. Culture sampling is best taken from the edges of progressive lesions and blister fluid, do smear examination, and perform aerobic and anaerobic bacterial culture respectively. Determination of the presence of streptococcal-induced antibodies in the blood (hyaluronidase and deoxyribonuclease B released by streptococci, which produce high titers of antibodies) can help in the diagnosis.