A Super-Antigen-Mediated Mimic of Acute Appendicitis

Bradley Laine Manning III, MD*; Patrick Schlievert, PhD and Loreen Herwaldt, MD, University of Iowa, Iowa City, IA

Meeting: Hospital Medicine 2016, March 6-9, San Diego, Calif.

Abstract number: 663

Categories: Adult, Clinical Vignettes Abstracts, Finalist

Keywords: , , ,

Case Presentation: A 23 year-old man with schizophrenia presented to the emergency department complaining of nausea, vomiting, headache, and subjective fever, followed by acute onset of right lower quadrant abdominal pain. His medications included chlorpromazine and benztropine. Vital signs: temperature 39 degrees C, pulse 155, respirations 18, and blood pressure 116/58. Admission exam was remarkable only for marked right lower quadrant (RLQ) tenderness to palpation. HIs white blood cell count was 14400/microliter, with 89.3% neutrophils. Liver function tests and basic metabolic panel were normal. CT scan of the abdomen and pelvis revealed a normal appendix and scattered subcentimeter lymph nodes in the RLQ mesentery. Admission blood cultures were negative at 5 days. The patient received intravenous normal saline and empiric piperacillin/tazobactam. General surgery was consulted. The next morning, the patient’s severe RLQ pain, fever, and leukocytosis persisted. The patient told an infectious disease consultant that his headache had resolved, and he had new oset of chills, soaking sweats, and sore throat. Oropharyngeal exam revealed very large tonsils with purulent discharge, a faint erythematous lacy rash on the back, and erythema on the upper torso that blanched to touch. The tonsillar exudate was cultured and grew penicillin-susceptible Streptococcus pyogenes, which produced super-antigenic exotoxins A, B, and C. His antibiotic treatment was changed from piperacillin/tazobactam to oral amoxicillin. The patient clinically improved.

Discussion: More common in children, mesenteric adenitis (MA) is a rare but recognized mimic of acute appendicitis in adults. MA has been associated with streptococcal pharyngitis.  This patient met radiographic criteria for MA, with 3 lymph nodes >5mm in the smallest diameter, but his lymphadenopathy was less dramatic than that seen in most cases of MA. We theorize that the superantigens produced by the S. pyogenes incited immune cell activation with massive pro-inflammatory cytokine production, leading to enlargement of the mesenteric lymph nodes, RLQ pain, and sepsis. Streptococcal pyrogenic exotoxins A, B, and C are associated with streptococcal toxic shock syndrome, and their presence likely explains the severity of this patient’s illness.

Conclusions: Appendicitis with sepsis is generally a surgical emergency, but non-operative conditions such as MA can mimic appendicitis. Clinicians must consider such conditions when a CT scan rules out acute appendicitis. Repeat interview and examination may help clinicians reach the correct diagnosis. Streptococcal pharyngitis usually does not produce abdominal pain and sepsis, but bacterial superantigens can mediate an intense inflammatory response. Clinicians should suspect super-antigen producing S. pyogenes in unusually severe cases.

To cite this abstract:

Manning BL III, Schlievert P, Herwaldt L. A Super-Antigen-Mediated Mimic of Acute Appendicitis. Abstract published at Hospital Medicine 2016, March 6-9, San Diego, Calif. Abstract 663. Journal of Hospital Medicine. 2016; 11 (suppl 1). https://www.shmabstracts.com/abstract/a-super-antigen-mediated-mimic-of-acute-appendicitis/. Accessed February 25, 2020.

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