Epidemiology of hidradenitis suppurativa and inflammatory bowel disease: are these two disease associated?

Hidradenitis suppurativa and inflammatory bowel disease are chronic inflammatory diseases mainly affecting young people. Their aetiology is complex and multifactorial and numerous case series have shown that the two diseases can manifest concurrently, although the strength of this association varies widely among distinct reports. An additional problem is the difficulty of distinguishing between cutaneous Crohn disease and hidradenitis. In the last few years, epidemiological cohort studies have revealed that 1.2%-23% of inflammatory bowel disease patients also have hidradenitis suppurativa. This wide variability is influenced by geographical variables and the biases inherent in the distinct data collection methods, among other factors. There is a clear predominance of Crohn disease over ulcerative colitis. When hidradenitis suppurativa and inflammatory bowel disease manifest concurrently, the bowel disease is more severe and shows a predominance of colon involvement.