Hidradenitis suppurativa: impact of environmental factors and new treatment options

Hidradenitis suppurativa (HS) is a chronic and diverse skin disease characterized by recurrent inflammation in body folds. It predominantly affects women, and its cause is complex and multifactorial. HS has a significant impact on the quality of life and is challenging to treat due to its complexity.The first part of this thesis focuses on understanding the epidemiology of HS, the lifestyle of patients, and their mental health. A study of 135,950 participants revealed that the prevalence of HS in Northern Netherlands was higher than previously thought, at 2.1%. HS patients had a lower socioeconomic status and were more likely to smoke. Furthermore, new associations were discovered between HS and conditions such as fibromyalgia and irritable bowel syndrome.Chapter three examined the lifestyle of HS patients and found lower scores for healthy nutrition and physical activity among them. This suggests that a healthy lifestyle may be protective against HS and underscores the need for prevention strategies.Chapter four investigated the mental health of HS patients and found a higher prevalence of depression, anxiety, and loneliness. However, there was no link between developing HS and mental health, indicating shared causes.Chapter five focused on the survival of biological treatments (adalimumab and infliximab) in HS patients. The study showed that the effectiveness of these treatments was limited, primarily due to ineffectiveness.Chapter six explored the use of retinoids in HS patients and found similar survival rates for isotretinoin and acitretin after 12 months. Some HS phenotypes may respond better to acitretin.The final chapter examined the use of guselkumab, a biological treatment, in HS. Approximately 65% of patients showed clinical improvement after 16 weeks of treatment. However, there were no consistent correlations between clinical and molecular responses.In summary, these studies demonstrate that HS is underdiagnosed, and more attention is needed for early diagnosis and treatment. A multidisciplinary approach, including consideration of lifestyle and mental health, is crucial. Treatment options vary, but biological treatments have limited effectiveness. Future research is needed to develop better treatment strategies for this complex condition