There is no association with ANCA, but about 30% of people with PAN have chronic hepatitis B and deposits containing HBsAg-HBsAb complexes in affected vessels, indicating an immune complex–mediated cause in that subset. The cause remains unknown in the remaining cases; there may be causal and clinical distinctions between classic idiopathic PAN, the cutaneous forms of PAN, and the PAN associated with chronic hepatitis.[3] In the pediatric population, cutaneous PAN is frequently associated to streptococcal infections, and positive streptococcal serology is included in the diagnostic criteria.[8]
No specific lab tests exist for diagnosing polyarteritis nodosa. Diagnosis is generally based on the physical examination and a few laboratory studies that help confirm the diagnosis:
A patient is said to have polyarteritis nodosa if he or she has three of the 10 signs known as the 1990 American College of Rheumatology (ACR)[9] criteria, when a radiographic or pathological diagnosis of vasculitis is made:
In polyarteritis nodosa, small aneurysms are strung like the beads of a rosary,[5] therefore making "rosary sign" an important diagnostic feature of the vasculitis.[6] The 1990 ACR criteria were designed for classification purposes only. Nevertheless, their good discriminatory performances, indicated by the initial ACR analysis, suggested their potential usefulness for diagnostic purposes as well. Subsequent studies did not confirm their diagnostic utility, demonstrating a significant dependence of their discriminative abilities on the prevalence of the various vasculitides in the analyzed populations. Recently, an original study, combining the analysis of more than 100 items used to describe patients' characteristics in a large sample of vasculitides with a computer simulation technique designed to test the potential diagnostic utility of the various criteria, proposed a set of eight positively or negatively discriminating items to be used as a screening tool for diagnosis in patients suspected of systemic vasculitis.[11]
In this disease, symptoms result from ischemic damage to affected organs, often the skin, heart, kidneys, and nervous system. Generalised symptoms include fever, fatigue, weakness, loss of appetite, and weight loss. Muscle and joint aches are common. The skin may show rashes, swelling, ulcers, and lumps.[citation needed] Palpable purpura and livedo reticularis can occur in some patients.
Nerve involvement may cause sensory changes with numbness, pain, burning, and weakness (peripheral neuropathy). Central nervous system involvement may cause strokes or seizures. Kidney involvement can produce varying degrees of kidney failure, such as hypertension, edema, oliguria, and uremia.[citation needed] Involvement of the arteries of the heart may cause a heart attack, heart failure, and inflammation of the sac around the heart (pericarditis).