Polyarteritis nodosa with life-threatening intracranial aneurysms in a child, and treatment with infliximab

Background. Polyarteritis nodosa (PAN) is a rare and serious form of systemic necrotizing vasculitis that predominantly affects medium and small-sized arteries, with central nervous system involvement being particularly uncommon. Treatment strategies are tailored according to the extent and severity of the disease. While conventional therapy includes glucocorticoids and conventional disease-modifying-rheumatic drugs (cDMARDs), biologic agents may be critical for severe and refractory cases. Case. We report a case of systemic PAN in a 7-year-old girl with no prior medical history, who presented with fever, abdominal pain, and altered mental status. Initial investigations with cranial MRI and echocardiography suggested encephalitis and myocarditis, respectively. Positive SARS-CoV-2 antibodies in both cerebrospinal fluid and serum oriented the diagnosis towards multisystem inflammatory syndrome in children. Despite intensive conventional therapies with glucocorticoids, cDMARDs, and intravenous immunoglobulins, the patient's condition deteriorated. Elevated von Willebrand factor levels, hypertension, and proteinuria emerged, along with stable intracranial hemorrhage and abdominal organ infarctions on imaging, leading to the diagnosis of PAN. Cyclophosphamide was added to the treatment regimen. Three cranial aneurysms were identified on selective conventional cranial angiography. Following angiography, severe intraparenchymal bleeding was detected, leading to emergency cranial surgery. Unresponsiveness to conventional therapeutics led to treatment escalation with a tumor necrosis factor inhibitor, infliximab, resulting in clinical stabilization and allowing for successful endovascular coil embolization. Conclusion. This case highlights the importance of considering a tumor necrosis factor inhibitor, infliximab, in severe PAN with involvement of intracranial aneurysm.