A 65-year-old woman with history of hypertension and diabetes mellitus presented to ER with 3-day worsening abdominal pain that she was experiencing for about 4 months. Pain was sharp, mainly in periumbilical region and lower abdomen, associated with several episodes of vomiting, non-bloody diarrhea for two days, weakness and myalgia. On examination, she had persistently elevated diastolic blood pressure, abdominal distention and generalized abdominal tenderness, otherwise, exam was negative. Blood work and abdominal ultrasound were normal. She was diagnosed with viral gastroenteritis and was treated conservatively with IV fluids, bowel rest and pain medications but her symptoms did not improve. Abdominal Computed tomography (CT) without contrast was then done and showed nonspecific stranding around the pancreas and kidneys. CT angiogram of abdomen and pelvis was suggestive of vasculitis and/or embolic phenomena involving numerous intra-abdominal arteries including superior/ inferior mesenteric, hepatic and distal renal arteries. It also showed a pseudoaneurysm in the hepatic hilum, bilateral ischemia involving renal cortices and necrotizing pancreatitis (image). Other lab tests including cryoglobulins, C3, C4, antineutrophil cytoplasmic antibodies (ANCA), antinuclear antibody, double-stranded DNA, serum and urine protein electrophoresis (SPEP and UPEP), human immunodeficiency virus, anti cardiolipin antibody, lupus anticoagulant and creatinine phosphokinase (CPK) were all negative. CT chest showed no features of pneumonitis or granulomatous disease. Based on the whole clinical scenario and CT imaging, a diagnosis of Polyarteritis Nodosa (PAN) was made as per American college of rheumatology criteria, so treatment with prednisone and cyclophosphamide was started. Repeat CT angiography 5 months later showed interval clearing of all abnormalities since prior study (image).
Discussion:
PAN is a systemic necrotizing vasculitis that basically involves medium sized muscular arteries with possible involvement of small arteries. PAN is a quite rare disorder with an estimated prevalence of 2 to 33 per million persons. PAN can affect any organ but has a unique tendency to spare the lungs. Patients mainly present with systemic symptoms and signs of multi-organ involvement. The pathogenesis of PAN is not well understood but one of the proposed mechanisms is immune complex mediated inflammation of arteries resulting in luminal narrowing and reducing blood flow. There is no diagnostic lab test for PAN and unlike some other types of vasculitis, PAN is not associated with ANCA. Because of the rarity of this disease and severity of side effects related to treatment, the diagnosis should be confirmed by biopsy if possible.
Although limited pancreatic infarction is common in PAN and GI manifestations have been noted in up to a third of patients with PAN, necrotizing pancreatitis is very rare and carries a poor prognosis. Our case is unique as the patient presented with both necrotizing pancreatitis as well as infarcts in the colon and renal cortices which is very uncommon.
Conclusions:
PAN should be considered as one of the rare causes of idiopathic acute necrotizing pancreatitis. This patient’s scenario emphasizes the importance of having a broad spectrum of differential diagnosis when facing a common clinical encounter as abdominal pain. Timely diagnosis and early initiation of proper therapy are crucial to decrease morbidity and mortality.
