Is hidradenitis suppurativa associated with anaemia?: a population-based and hospital-based cross-sectional study from Denmark.
Chronic inflammatory diseases may be associated with anaemia of inflammation. Hidradenitis suppurativa is a chronic inflammatory dermatological disease associated with metabolic comorbidities, low quality of life and fatigue. Anaemia may cause fatigue, and it has been hypothesized that HS-related fatigue may be partly due to anaemia. Our objective was to investigate a possible association between HS and anaemia. We performed a hospital-based and population-based cross-sectional study investigating the red blood cell profile, i.e. haemoglobin. We identified a total of 32 hospital HS individuals, 430 population HS individuals and 20,780 population non-HS control individuals. The age-sex-smoking-adjusted analyses showed no differences in the haemoglobin level of the HS groups vs. the control group. Analyses of the anaemic subgroup of HS individuals revealed that 60% had normocytic anaemia and 40% microcytic anaemia, in concordance with anaemia of inflammation. In contrast to our hypothesis, this study showed that HS is not associated with anaemia. Thus, anaemia may not be the cause of the described fatigue in HS patients. Furthermore, the results indicate that if an HS patient does suffer from anaemia it is most likely to be normocytic or microcytic and thus compatible with anaemia seen in other chronic inflammatory disorders.