Spontaneous isolated superior mesenteric artery dissection (SISMAD) is a rare vascular condition where the superior mesenteric artery is affected by dissection without involving other arteries. Its incidence is estimated at 0.06% to 0.08% globally. The possible causes include polyarteritis nodosa (PAN), an autoimmune disease affecting medium-sized arteries. SISMAD can manifest with various clinical presentations, from asymptomatic to acute bowel ischemia, warranting consideration when common causes of acute abdomen are ruled out.

This is the case of a 44-year-old female Filipino, hypertensive, who complained of abdominal pain, initially managed as intestinal amoebiasis. Abdominal examination showed a soft, non-tender abdomen with no guarding, making the symptoms disproportionate to physical examination. Due to persistence of symptoms despite a full antibiotic course, further workup was done. Computed tomography (CT) scan of the whole abdomen with contrast revealed an isolated dissection of the proximal superior mesenteric artery (SMA) with thrombosis which was confirmed on CT angiography. The diagnosis of PAN was established based on the correlation of clinical presentation, laboratory findings and imaging results. Conservative management was done and to address the thrombosis, anticoagulation with heparin was initiated. The patient was also given methylprednisolone pulse therapy and cyclophosphamide with good response. Resolution of symptoms noted and she was eventually discharged improved.

SISMAD and PAN are independently rare conditions. This unique case involved both diseases in a 44-year-old Filipino female, and to date, there have been no reported similar cases worldwide. Early diagnosis of the disease requires a high degree of suspicion and pattern recognition. This is crucial for timely treatment and improved prognosis. Furthermore, close surveillance is important to identify potential relapses even after symptom resolution.