Necrotizing fasciitis is a severe soft tissue infection characterized by rapidly progressing necrosis, involving subcutaneous tissues. This rare condition carries a high mortality rate and requires prompt diagnosis and urgent treatment with radical debridement and antibiotics; but early diagnosis, which is essential to successful treatment, remains a challenge.Physical examination findings, preoperative and operative findings, histopathological results of the structure, and follow-up results of the patient are discussed with related reports.A 15-month old girl had a history of trivial perineal dermatitis after treatment of anemia and pneumonia. Perineal dermatitis progressed fastly as necrotizing fasciitis which was successfully managed with intensive medical treatment, surgical debridement and reconstructive surgery.Lack of cutaneous findings early in the disease makes the diagnosis challenging, so a high suspicion is essential. Recovery of the patient from this life-threatening condition needs a multi-disciplinary approach involving pediatrics, pediatric surgery, and plastic and reconstructive surgery.