Spontaneous accessory renal artery aneurysm rupture as a first presentation of polyarteritis nodosa: a case report and review of literature.

Introduction: Polyarteritis nodosa (PAN) is a systemic necrotizing vasculitis primarily affecting medium-sized vessels. It has several clinical manifestations, including renal, gastrointestinal, cutaneous, neurologic, and general symptoms, but it is not associated with pulmonary manifestations. PAN mainly affects individuals aged 40-60 years, with a male predominance. Although the underlying cause of this disease remains unclear, several triggers can be associated with it such as hepatitis B virus. Diagnosis typically requires an organ biopsy or angiography revealing microaneurysms or stenotic lesions. The overall prognosis can improve with early diagnosis and administration of immunosuppressants. However, it remains a potentially life-threatening diagnosis with a mortality rate of 24.6% at 5 years for severe cases. We presented a rare case of PAN with severe renal and gastrointestinal involvement at presentation. Case presentation: A 21-year-old male presented with sudden severe right flank pain radiating to the back. He was noted to have reticular purple skin lesions on his abdomen and lower legs. Clinical and laboratory findings indicated that he had a hemorrhagic shock. A contrast-enhanced computed tomography (CT) scan of the abdomen and pelvis revealed a ruptured, partially thrombosed pseudoaneurysm of an accessory right renal artery with acute retroperitoneal hemorrhage, splenic infarcts, and two lower mesenteric artery aneurysms. Selective coil embolization of the ruptured artery was successfully conducted. Notably, the patient reports a 1-year history of intermittent abdominal pain, bilateral foot pain, and livedo reticularis, alongside left testicular pain managed with varicocelectomy. During the hospital stay, the patient developed progressive bilateral lower limb weakness that nerve conduction studies revealed it as mononeuritis multiplex. These combined findings were pointing toward PAN diagnosis. Therefore, the patient was started on pulse steroid and cyclophosphamide therapy. However, his abdominal pain worsened requiring surgical exploration with extensive bowel resection, after which plasmapheresis was commenced. Discussion: After our patient presented with life-threatening retroperitoneal bleeding, CT scan revealed that an accessory renal artery had ruptured, and also revealed the hidden cause of his chronic, recurrent, self-resolving attacks of severe abdominal pain, which were investigated multiple times by endoscopy without appropriate diagnosis. The final diagnosis of PAN was supported by the presence of livedo reticularis, testicular ischemia, chronic abdominal pain, and mononeuritis multiplex, fulfilling four diagnostic criteria of the American College of Rheumatology for PAN. Renal involvement in PAN can be in up to 75% of cases. However, rupture of accessory renal artery aneurysms is infrequent and it was the first presenting symptom of our patient. Similarly, GI complications are observed in 50% of patients, which can progress to life-threatening ischemia and gangrene, as seen in this case. Treatment involved corticosteroids and cyclophosphamide as an induction therapy based on the 2011 revised Five-Factor Score (FFS). The addition of plasma exchange therapy in this patient was due to the catastrophic complications of PAN. Eventually, the patient became clinically stable with an expected 5-year survival rate of 65.0% according to his FFS ≥2. Therefore, careful follow-up is necessary. Conclusion: Even though vascular aneurysms in PAN have a long history, they are more often linked to gradual development rather than to catastrophic events. Acute rupture resulting in hemorrhagic shock is rarely the initial sign of PAN. Rare reports of renal artery rupture in PAN highlight the significance of having a high level of clinical suspicion in young patients with unexplained vascular events. Early diagnosis and rapid management, including immunosuppressive therapy and plasmapheresis, are crucial in preventing severe outcomes. Despite a poor prognosis associated with severe disease features, careful management can stabilize the patient, although long-term follow-up remains essential.