A 35-year-old man presents to emergency department with complaints of left-sided substernal chest pain and dyspnea that has started 30 minutes ago. The pain is stable in intensity, is not exacerbated by inspiration or movement and radiates to the left arm and lower jaw. The patient's medical history includes postprandial abdominal pain, significant weight loss (>10 pounds) during the last 2 months, muscular aches, night sweats and a recent episode of testicular torsion. Vital signs are as follows: 80/50 mmHg, 97.7°F, 110 bpm, 90% blood O2 saturation in room air and 20 respirations/min. Electrocardiogram (ECG) shows ST elevation in leads V1 and V2, arterial blood gas (ABG) values are completely normal and cardiac Troponin I is elevated. Invasive coronary angiography reveals multiple microaneurysms at the proximal left anterior descending artery, with thrombus formation occluding its entire lumen. The lesions are eventually treated with percutaneous coronary intervention (PCI) and the patient recovers. Considering the medical history of the patient, mesenteric angiography is ordered as well. It demonstrates multiple microaneurysms at the superior mesenteric artery. Diagnosis of polyarteritis nodosa is made, and intravenous treatment with methylprednisolone and cyclophosphamide is started.
Which of the following mechanisms characterizes polyarteritis nodosa?
The correct answer is: B. Segmental transmural arterial wall inflammation with fibrinoid necrosis
Polyarteritis nodosa (PAN) is a systemic necrotic vasculitis that affects primarily medium-sized arterial vessels. PAN is not associated with antineutrophil cytoplasmic antibodies (ANCA) and its prevalence is higher in middle-aged men.1,2 Although most cases of PAN are idiopathic, secondary causes include hepatitis B virus (HBV), hepatitis C virus (HCV) and hairy cell leukemia. HBV-associated PAN is mediated through Type III hypersensitivity reaction with deposition of immune-complexes in the vessel wall, causing inflammation.1,2 Affected vessels become thickened through intimal proliferation and weakened in multiple locations predisposing to formation of aneurysms.
The main histopathological characteristic of the disease is a segmental transmural arterial wall inflammation with fibrinoid necrosis of the vessels of the affected organ.1 Kidneys are the most commonly affected organs. PAN can also affect the heart, the skin and the peripheral nervous, musculoskeletal and gastrointestinal systems.2 Patients usually present with long-standing hypertension due to renal involvement and systemic signs of the disease (fatigue, fever, weight loss, night sweats).
Vasculitis of coronary arteries is common if the heart is involved and may lead to thrombosis of coronary arteries causing myocardial infarction.3 Similarly, mesenteric arteritis could cause "intestinal angina" and postprandial abdominal pain. Treatment includes the combined use of oral glucocorticoid and immunosuppressive (cyclophosphamide) therapy.1
Presence of giant cells in the arterial wall (Answer A) characterizes giant cell arteritis (GCA), the most common vasculitis in patients older than 65 years. GCA affects large vessels, like the superficial temporal artery and main branches of the aorta.
Non caseating granuloma formation (Answer C) is the main histopathological characteristic of granulomatosis with polyangiitis and eosinophilic granulomatosis with polyangiitis. The clinical course and the organs being primarily affected, differ between this vasculitis and PAN.
IgA deposition in arterial wall (Answer D) is the main characteristic of skin biopsy in Henoch-Schönlein purpura (HSP). HSP is an IgA-mediated vasculitis that most commonly affects children. Purpuric rash in buttocks and lower limbs, arthritis and abdominal pain constitute the "classic triad" of HSP.
PAN is a multisystem necrotizing vasculitis that affects medium-sized vessels and is associated with HBV, HCV and hematologic malignancies. Biopsy specimens of affected organs show segmental transmural arterial wall inflammation with fibrinoid necrosis. PAN-associated myocardial infarction is mediated through coronary vasculitis, although it is an atypical presentation of the disease.1-3
Mahr A, Guillevin L, Poissonnet M, Ayme S. Prevalences of polyarteritis nodosa, microscopic polyangiitis, Wegener's granulomatosis, and Churg-Strauss syndrome in a French urban multiethnic population in 2000: a capture-recapture estimate. Arthritis Rheum 2004;51:92-99.
De Virgilio A, Greco A, Magliulo G, et al. Polyarteritis nodosa: A contemporary overview. Autoimmun Rev 2016;15:564-70.
Kastner D, Gaffney M, Tak T. Polyarteritis nodosa and myocardial infarction. Can J Cardiol 2000;16:515-18.