Case Presentation: A 69 year old woman presented to the hospital with 2 days of progressively worsening right lower leg pain and rash. Other symptoms included persistent nausea & vomiting following a recent episode of gastroenteritis. Exam demonstrated normal vital signs and bilateral lower extremity edema extending to the knees with apparently equal bilateral tenderness. Right lower extremity had a non-raised, non-palpable, purplish-red petechiae-like rash. Laboratory analysis showed elevated creatinine (2.01 mg/dL), elevated BUN (35 mg/dL), thrombocytopenia at 61,000/μL (165,000-366,000/μL) and leukocytosis of 13,200/μL. CT scan showed diffuse subcutaneous right leg edema, so the patient was admitted and empirically started on piperacillin/tazobactam and Linezolid. Within a few hours, the patient rapidly decompensated, developing an extensive petechial rash along the right lower extremity with new crepitus and bullae, and profound hypotension (66/44 mm Hg) unresponsive to fluids or norepinephrine. Due to concern for necrotizing soft tissue infection, she was emergently taken to the OR for debridement of her right lower extremity.
Discussion: Despite its variable presentation, NSTI typically presents acutely over hours, often following an inciting event such as trauma. Common presentations involve acute onset of erythema, edema, fever, and bullae or overt necrosis, which helps early diagnosis and, thereby, prompt initiation of treatment. However, in our patient, lack of fever, subacute presentation over days, less common skin features like petechiae, lack of inciting event, and positive GI symptoms made NSTI a more challenging diagnosis. Culture from the surgical debridement grew Streptococcus dysgalactiae, which is rare compared to the more common Group A Streptococcus or Methicillin-resistant Staph. aureus. Group C/G strep represents normal skin flora and often causes a similar disease process to GAS in NSTIs. This may be partially due to the horizontal transfer of genes between genomes, including virulence factor and exotoxin genes. This link may also describe the gastroenteritis which preceded NSTI in our case, as GAS exotoxins have been attributed with causing GI symptoms in the setting of NSTI.
Conclusions: NSTIs often present with a variety of symptoms and be caused by a variety of microorganisms. With a mortality rate of 20-40%, prompt diagnosis and appropriate treatment of NSTI is crucial to long-term survival. As such, there should be a low threshold to include NSTI on differential diagnoses when evaluating patients with extremity pain and accompanying skin changes. We presented an atypical case of lower extremity NSTI. However, atypical presentation or not, treatment for NSTI requires immediate antibiotic therapy with emergent surgical debridement for good patient outcomes.
