In polyarteritis nodosa, small aneurysms are strung like the beads of a rosary, therefore making this "rosary sign" an important diagnostic feature of the vasculitis. The 1990 ACR criteria were designed for classification purposes only, but 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. Differential diagnosis
Polyarteritis nodosa rarely affects the blood vessels of the lungs and this feature can help to differentiate it from other vasculitides that may have similar signs and symptoms (e.g., granulomatosis with polyangiitis or microscopic polyangiitis). Treatment
Treatment involves medications to suppress the immune system, including prednisone and cyclophosphamide. When present, underlying hepatitis B virus infection should be immediately treated. In some cases, methotrexate or leflunomide may be helpful. Some patients have entered a remission phase when a four-dose infusion of rituximab is used before the leflunomide treatment is begun. Therapy results in remissions or cures in 90% of cases. Untreated, the disease is fatal in most cases.
Non-systemic vasculitic neuropathy
Non-systemic vasculitic neuropathy (NSVN) is a diagnosis of elimination. When no systemic illness can be found, yet evidence of a vasculitic neuropathy exists, a diagnosis of non-systemic vasculitic neuropathy is made. It is a single-organ problem. A nerve biopsy is required in order to make the diagnosis of non-systemic vasculitic neuropathy. There are distinct subtypes of NSVN with evolving categorisation in the literature. Currently accepted subtypes are:
Classical distal-predominant NSVN
Wartenberg migratory sensory neuropathy
Post-surgical inflammatory neuropathy
Diabetic radiculoplexus neuropathy (lumbosacral, thoracic or cervical predominant)
Neuralgic amyotrophy
Non-systemic skin/nerve vasculitis (for example, cutaneous PAN)

Classical distal-predominant NSVN
There is an ongoing debate over this categorisation, particularly its overlap with the condition non-diabetic radiculoplexus neuropathy. This neuropathy involves a clinical picture where the nerve damage is distally predominant as demonstrated in a nerve biopsy. Warternberg migratory sensory neuropathy
Warternberg migratory sensory neuropathy is typically a multi-focal neuropathy where there is pure sensory deficits. It is characterised by sudden-onset and chronicity as well as having a propensity for relapse. It generally resolves slowly with time. Postsurgical inflammatory neuropathy
Postsurgical inflammatory neuropathy is typically a multi-focal neuropathy which manifests thirty days after a surgical procedure. It mostly presents with motor and sensory symptoms. It is generally a self-limiting condition that has resolved with and without treatment. Diagnosis
Diagnosis of a vasculitic neuropathy depends on whether the patient first presents with multiple symptoms pointing at a systemic disorder or else primary neuropathic complaints. In the former case the patient is more likely to be assessed first by a rheumatologist and in the latter a neurologist or neurosurgeon.