A retrospective study comparing the phenotype and outcomes of patients with polyarteritis nodosa between UK and Turkish cohorts.

There is a need for better definition of polyarteritis nodosa (PAN) subphenotypes and the influence of ethnicity and geography. This study is aimed to study the demographic and clinical features of PAN cohorts from the UK and Turkey (TR) and to compare and contrast disease characteristics. A retrospective survey of databases from two vasculitis centres between 1990 and 2016 for PAN patients fulfilling the EMEA Vasculitis Classification algorithm. All paediatric-onset adult patients met the Ankara 2008 (EULAR/PReS endorsed) criteria for childhood PAN. Those with typical angiographic and/or histopathologic findings consistent with PAN were included. 93 (M/F: 51/42) patients (UK: 47, TR: 46) were included. Three were HBV-related, 20 (21.5%) had paediatric onset and 16 (16.5%), cutaneous PAN. TR patients had younger age of disease onset 44 (28.5-59.0) vs. 24.5 (11.8-40.5), p = 0.002. Twelve (26%) of TR patients had monogenic disease (Familial Mediterranean Fever association (n = 7), deficiency of adenosine deaminase 2, DADA2, (n = 5). No difference was found in phenotype between paediatric and adult onset patients except for frequency of cutaneous lesions (p = 0.002). During a median 67.5 (32-126) months follow-up, 13 patients died (12.7% in UK vs. 15.2% in Turkish cohorts). No difference was found between two cohorts in relation to relapse rate, death and vasculitis damage index. This study defined a diagnosis of PAN according to the EMEA algorithm. The TR group had a younger age of disease onset and more cases of monogenic disease; however, disease extent, relapse rate, damage index and death rates were similar between groups.