Acute Diverticulitis as an Atypical Presentation of Alpha-Gal Syndrome.

Alpha-gal syndrome (AGS) is an immunoglobulin E (IgE) mediated hypersensitivity reaction caused by tick bites. The body's immune response to tick bites can lead to the production of anti-alpha-gal IgE antibodies, disrupting the normal oral tolerance to food allergens. AGS typically results in delayed anaphylaxis after consuming red meat or certain medications and immediate anaphylaxis following tick bites; however, isolated gastrointestinal manifestations are increasingly being reported. We present a case of a 38-year-old female patient with a history of AGS who developed acute sigmoid diverticulitis with associated pelvic abscess, likely related to her AGS. Despite initiation of broad-spectrum intravenous antibiotics, the patient experienced persistent severe abdominal pain requiring diagnostic laparoscopy; however, bowel resection was ultimately avoided. The patient improved with continued intravenous antibiotics and had complete symptom resolution on follow-up. This case highlights the expanding gastrointestinal spectrum of AGS and raises the concern of an association between AGS-related immune dysregulation and inflammatory colonic pathology such as diverticulitis. Recognition of atypical gastrointestinal presentations of AGS is essential to reduce delays in diagnosis and misclassification as other gastrointestinal disorders.