Necrotizing fasciitis masked by diabetes mellitus: a case report

Necrotizing fasciitis (NF) is a life-threatening soft tissue infection. In patients with diabetes mellitus, diagnosis is often challenging due to atypical presentations caused by diabetic neuropathy and vascular complications. We report a case of extensive NF in a patient with type 2 diabetes who presented with minimal pain and atypical cutaneous findings despite extensive deep tissue involvement, aiming to reinforce the clinical warning that in this high-risk population, the absence of classic symptoms should not lower suspicion for NF. A 64-year-old Han Chinese man with poorly controlled type 2 diabetes (HbA1c 9.50%) and peripheral neuropathy was admitted to the Department of Endocrinology on August 13, 2025, with a 2-day history of general fatigue and worsening dull pain in the left thigh and buttock. He recalled minor trauma to the left hip one month prior. Physical examination revealed left lower extremity weakness (grade 3/5), reduced pinprick and vibration sensation below the knees, and unremarkable skin changes except for mildly increased local temperature. Notably, the patient’s pain severity was disproportionate to the extensive clinical findings, a finding likely attributable to reduced nociception from diabetic peripheral neuropathy. Laboratory findings showed leukocytosis (15.26 × 10⁹/L), elevated C-reactive protein (242.30 mg/L), and ketonuria. The LRINEC score was calculated as 6, supporting the diagnosis of NF. Ketonuria in the setting of SGLT2 inhibitor use raised the possibility of euglycemic diabetic ketoacidosis (euDKA). On August 14 (hospital day 2), empirical ceftriaxone was initiated. However, systemic symptoms worsened and swelling expanded, with subcutaneous crepitus detected on deep palpation despite only mild pain reported. Consequently, on August 15 (hospital day 3), the regimen was escalated to piperacillin-tazobactam (4.5 g intravenously every 8 h) combined with tinidazole (0.8 g intravenously daily). On August 16, the patient was transferred to the Department of Anorectal Surgery and underwent emergency surgery; the piperacillin-tazobactam plus tinidazole regimen was continued intraoperatively and postoperatively. Intraoperative findings revealed extensive fascial necrosis with foul-smelling purulent discharge. Cultures grew methicillin-sensitive Staphylococcus aureus (MSSA). Following susceptibility confirmation, the regimen was de-escalated to piperacillin-tazobactam monotherapy (4.5 g every 8 h). The infection was controlled, and the wound healed gradually. At 3-month follow-up, the patient remained stable with no signs of recurrence, adequate limb perfusion, and no progression of iliac artery stenosis. This case demonstrates that necrotizing fasciitis (NF) in patients with type 2 diabetes complicated by diabetic peripheral neuropathy can present with only minimal pain and atypical cutaneous findings. Given that NF is characterized by difficulty in early diagnosis and rapid progression, the key educational message of this case is that, in this high-risk population, the absence of typical pain should not lower clinical suspicion for NF. A high index of suspicion, thorough palpation for crepitus, and early imaging are crucial for timely diagnosis. Once diagnosed, multidisciplinary management—including aggressive debridement, pathogen-directed antibiotics, glycemic control, and vascular assessment—is essential for optimal outcomes.