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. Possible causes include trauma, congenital connective tissue disorders, arteriosclerosis, and vasculitis such as polyarteritis nodosa (PAN). 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 a case of a 44-year-old female Filipino, 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 full antibiotic course, further work up 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. C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), cytoplasmic antineutrophilic cytoplasmic antibodies (ANCA) and perinuclear ANCA were both negative; antinuclear antibody (ANA), C3 and C4 levels were also unremarkable. The diagnosis of PAN was established based on the correlation of clinical presentation, laboratory findings, and imaging results. She was given methylprednisolone pulse therapy and cyclophosphamide with good response. Anticoagulation with heparin was initiated to address the thrombosis. The patient had complete bowel rest, pain management, intravenous hydration, and parenteral nutrition. Resolution of symptoms noted and was eventually discharged improved.

SISMAD and PAN are independently rare conditions. This unique case involved both diseases in a 44-year-old Filipino female. 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.