Polyarteritis nodosa (PAN) is a systemic vasculitis that mostly involves medium sized arteries, and sometimes involves small arteries ¹ . The prevalence of PAN is estimated to be 2 to 33 million individuals ^{2, 3} . The annual incidence in some areas of Europe estimate 4.4 to 9.7 per million population ⁴ . The diagnosis is most commonly made in middle-aged or older adults and increases with age, and its peak is in the sixth decade of life ² . Polyarteritis nodosa can mimic the clinical manifestations of Henoch-Schonlein purpura (HSP) that is newly named Immunoglobulin A-associated vasculitis (IgAV). It is difficult to differentiate between PAN and HSP (IgAV), at an early stage. If PAN is not diagnosed and treated at an early stage, it has a high morbidity ^{5, 6} . Considering that PAN is a rare disease and requires a high clinical suspicion for diagnosis, here, we report a case of PAN and the reasoning behind its diagnosis in our patient.

Unlike other vasculitis’s such as microscopic polyarthritis or Wegener’s, PAN is not associated with ANCA ⁷ . The organs most often affected in PAN are the skin, renal and GI tract. Cardiac involvement can manifest itself with hypertension, or even ischemic heart disease ⁸ . In the skin, PAN may manifest by erythematous nodules, livedo reticularis, ulcer, bullous or vesicular eruption and purpura ^{7, 9, 10} . Gastrointestinal symptoms that may be seen include abdominal pain, nausea, vomiting, melena, bloody or non-bloody diarrhea, and life-threatening gastrointestinal bleeding ¹¹ . One of the most common manifestations of patients with PAN is mononeuropathy multiplex that typically involves both motor and sensory deficits in up 70% of patients ^{7, 12} . Some of the patients have sensorineural hearing loss ¹³ Most cases of PAN are idiopathic, although hepatitis B virus infection, hepatitis C virus infection, and hairy cell leukemia are important in the pathogenesis of some cases ^{3, 4, 14, 15} . PAN can mimic the clinical manifestations of HSP (IgAV). It is difficult to differentiate between PAN and HSP (IgAV) at an early stage ⁵ . The biopsy pattern helps to differentiate between PAN and HSP (IgAV); in tissue studies of HSP (IgAV) leukocytoclastic vasculitis in postcapillary venules together with IgA deposition is observed ¹⁶ . As already mentioned, PAN is most commonly seen in middle-aged or older adults ³ , while HSP (IgAV) is a childhood disease that occurs between the ages of 3 and 15 years ¹⁷ . Neurologic manifestation in HSP (IgAV) is rare. Single reports and case series document neurologic manifestations including headaches, intracerebral hemorrhage, focal neurologic deficits, ataxia, seizures, and central and peripheral neuropathy in children with HSP (IgAV) ¹⁸ . According to EULAR/PRINTO/PRES classification criteria, there was no renal failure, arthralgia and arthritis in this patient, but basis on other item, HSP (IgAV) could be diagnosis ¹⁹ . In the present case, using clinical manifestations and laboratory tests, we excluded another differential diagnosis apart from PAN. Considering that PAN and HSP (IgAV) have narrowing clinical manifestation, we differentiated between the two diseases by age and neuropathy. However, although the diagnosis of the present patient is PAN, for a better diagnosis, immunofluorescence of the biopsy was needed, which is not available in our center. Finally, diagnosis and treatment of PAN are important. PAN should be considered in a patient with skin lesions and neurological impairment.

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