Clinical characteristics of hidradenitis suppurativa patients in Okinawa, Japan: Differences between East Asia and Western countries.

Hidradenitis suppurativa (HS) is a long-term inflammatory follicular disease. In Western countries, the prevalence of HS has been estimated to be 0.1-4% in the general population. In Okinawa Prefecture, the southernmost area of Japan, HS is more frequent than in other parts of Japan. The aim of this study is to elucidate the epidemiological features of HS patients in Okinawa, Japan, to determine the factors correlated with severity and to compare characteristics of HS patients in East Asia and Western countries. This study was a retrospective, single-center, case series study. Data of patients with HS diagnosed at the University of the Ryukyus Hospital from April 2010 to March 2019 were collected and compared with data of previous studies performed in Japan, Korea, France and the USA. There were 42 male and 16 female HS patients (age range, 15-76 years). The median modified Sartorius score was 49 (interquartile range, 87.3). A multivariate analysis indicated that disease duration was associated with the modified Sartorius score. The ratio of serum C-reactive protein to albumin was significantly correlated with disease severity (rs  = 0.64, P < 0.001). Overall, in East Asia, HS was more common in males, and very few patients had a family history of HS (1.7% vs 29.1%, P < 0.001) compared with Western countries. This study revealed the characteristics of HS patients in Okinawa and elucidated the differences between the epidemiology of HS in Western countries and East Asia. In addition, we found out factors that correlated with disease severity such as disease duration and serum C-reactive protein to albumin ratio.