Co-morbidities in hidradenitis suppurativa - cardiovascular disease and inflammatory bowel disease

Patients with hidradenitis suppurativa (HS) are at increased risk of multiple co–morbidities including major adverse cardiac events (MACE) and inflammatory bowel disease (IBD). While increased risk of MACE and IBD has been demonstrated in database and registry studies, visualisation of coronary artery disease has not been completed, the impact of treatment on cardiovascular risk biomarkers has not been reported and the optimal method of screening for IBD has not been determined. A prospective cross-sectional study was completed to address these knowledge gaps in this thesis. Patients were recruited sequentially from two dermatology clinics. In the cardiovascular disease arm of the study, patients were screened for traditional and non-traditional cardiovascular disease risk factors using questionnaires and serum markers. A subset of these sequential patients were invited to undergo coronary computed tomography angiography to identify the presence of coronary artery disease. Separate to this, a post-hoc analysis of the PIONEER I and II trials of adalimumab was completed to assess response of cardiovascular risk factors to treatment. In the IBD arm of the study, patients were screened using a sign/symptom-based questionnaire and asked to return a stool sample for faecal calprotectin testing. This thesis reports a high prevalence of traditional cardiovascular disease risk factors in addition to the novel cardiovascular disease risk factors; depression, anxiety, psychological distress, low socioeconomic status and systemic inflammation in a large cohort of patients with HS. In a pilot study of coronary computed tomography angiography, almost all patients had calcified and non–calcified plaque using artificial intelligence software for quantitative plaque analysis confirming the association of HS with increased risk of MACE. In addition, this thesis identifies that urate, homocysteine and growth differentiation factor–15 are biomarkers of cardiovascular risk factors and 10–year risk of MACE. Neutrophil/lymphocyte ratio, platelet/lymphocyte ratio, monocyte/lymphocyte ratio and systemic immune inflammation index are novel systemic inflammatory and cardiovascular risk biomarkers which are reduced by biologic treatment of hidradenitis suppurativa. Lastly, this thesis reports a prevalence rate of IBD of 7.3% in patients with HS attending hospital–based services. Routine faecal calprotectin screening did not identify any new occult IBD cases. The prevalence of HS in IBD, conversely, was higher at 16.4% using validated HS screening questions. Routine screening of all patients with HS for cardiovascular disease risk factors is warranted. Earlier intervention with biologic treatment may reduce cardiovascular risk. Routine screening for IBD may still be warranted but this thesis falls short of proving the beneficial effect of this with faecal calprotectin. Patients with IBD should be screened for HS given the high prevalence of disease.

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