Abstract

Background/Purpose: Systemic polyarteritis nodosa (PAN) is a predominantly medium size vasculitis  characterized by non granulomatous necrotizing vasculitis. We aimed to evaluate clinical, laboratory and imaging features of cutaneous (cut-) PAN and the PAN form  and to develop a new set of diagnostic criteria for cut-PAN in a large international pediatric vasculitis registry available on the PRINTO database.

Methods: We extracted from the PRINTO database all the patients who fulfilled the Ankara 2008-EULAR/PRES/PRINTO criteria for PAN. The cut-PAN patients as per the treating physician diagnosis were also extracted. To define clinical and laboratory characteristics who could help to differentiate cut-PAN  from PAN and univariate logistic regression analysis was performed.

Developing a new set of diagnostic criteria for cut-PAN: Principle component analysis were performed to detect best representative factors of cutaneous symptoms in cut-PAN patients. The one with the highest sensitivity and specificity in the generated models were accepted as diagnostic criteria in our study.

Results: There were 109 and 45 patients classified as PAN, and cut-PAN  respectively with a mean age at diagnosis of 9.47±3.59 years; and 9.12±3.83 years; respectively. The female/male ratio and ethnicity did not differ in the 2 subtypes. The cutaneous group had significantly less constitutional features and less acute phase reactant levels, as expected. The median values (IQR 25-75%) for the ESR and CRP for PAN were 78 (48-108) mm/h and 7.36 (2.76-15.03) mg/dL. Musculoskeletal features such as myalgia was present in 82 (75.2 %) patients with PAN and 18 (40.9%) patients with cut-PAN (p<0.001) both groups. As differentiating features skin infarcts were observed in PAN only and constitutional features, angiographic abnormalities, and organ involvement was not seen in any of the cut-PAN patients. Malaise, fever, severe headache, motor mononeuritis multiplex, sensory peripheral neuropathy, abdominal pain, and hematuria were the most statistically significant clinical characteristics able to differentiate these two entities.

New set of diagnostic criteria for cut-PAN is the absence of any organ involvement (constitutional and musculo skeletal symptoms  are acceptable) and presence of any of 4 cutaneous findings (Livedo reticularis, skin nodules, polymorphous exanthema, panniculitis). Sensitivity of proposed diagnostic criteria obtained from the existing database for cut-PAN  was calculated as 88.8%, specificity  97.8%,  positive  predictive  value 83.3%  and negative  predictive  value  98.6%.  

Conclusion: The large number of patients with other vasculitides and cutaneous PAN has enabled us to have a significant specificity and sensitivity for the suggested criteria. Furhter biological studies are needed to effectively differentiate the two entities.