DOI: 10.25934/pr00007872
title: Hidradenitis Suppurativa – a collaborative study of subtypes 

description: Personalized medicine (PM) is often thought to require the identification of a specific, measurable biomarker (i.e., a molecule found in blood, other body fluids, or tissues that is indicative of a disease) that reflects the activity of a key pathogenic (causing, or capable of causing disease) step preferably unique to the disease at hand. In reality, PM can be – and is being – practiced based on clinical biomarkers by clinical experts, who use history and clinical observation to gauge which treatment carries the least risk for the patient.

Hidradenitis Suppurativa (HS) is a chronic skin disease, which presents as inflamed nodules and abscesses of a non-infectious etiology (i.e. the cause or origin of the disease). The lesions cause scarring, and often evolve into chronic suppurating [to form or give out a thick, yellow liquid (pus) because of infection] skin tunnels in the affected areas, i.e., armpits, folds under the breasts, or groin. Treatment options for HS are limited and include antibiotics (rifampicin, tetracycline and clindamycin) as well as adalimumab, and/or surgery.

HS most often manifests around the third decade of life. HS prevalence estimates vary from 0.1-0.5% based on hospital register data to 1-2% based on self-reported data. This variation presumably reflects both the time it takes for the disease to be diagnosed, which is typically in the order of 7-10 years, fluctuations of disease severity and different degrees of HS severity with cases treated in hospital being the most severe.  

HS etiology remains elusive, but a high prevalence of other significant medical conditions including in particular a wide variety of metabolic and autoimmune conditions points in the direction of underlying immune dysfunction.

HS is associated with reduced health-related quality of life and with increased levels of suffering and stigmatization. Indeed, people with HS are at increased risk of alcohol abuse, depression, and anxiety. Compared to the general population people with HS are more than four times as likely to be smokers, more than three times as likely to be obese, and nearly twice as likely to be of low socioeconomic status, with even higher figures for those with the most severe disease. The general clinical presentation for HS patients is summarized by the fact that they have a statistically increased risk of all-cause death including suicide. 

The current treatment options are very limited with only one approved drug, adalimumab, for the therapy. Although much progress has been made in the management of HS, none of the drugs used offer an entirely satisfactory result leaving patients with a substantial unmet need for therapy. 

Finally, due to the delay in diagnosis and varying nature of the disease, it has been hinted that various clinical subtypes may exist further suggesting possible different etiology, treatment approaches and prognosis. HS is a complex disease in which genetics play a role, but a number of other factors are also prominent, e.g. composition of the microorganisms in the gut, hormonal factors, mechanical forces affecting the skin, obesity and tobacco. A purely genetically-based sub-classification may therefore not be sufficient for clinical use. Currently there is neither a generally accepted genetic nor clinical subclassification of HS. Subclassification of HS could lead the way for an optimized approach (personalized medicine) when clinically treating and managing HS. 

This is a multi-center cohort study. De-identified pre-specified phenotypical parameters from HS patients will be obtained from independent cohorts from academic centers and the industry. The data will then be pooled into a communal dataset. All datasets and definitions will be harmonized prior to data pooling. In the pooled communal dataset, the source of the original data will not be discerned. We aim to include data from up to 8000 patients (large powered cohort). Previous studies have only included 1000, and they have therefore been insufficiently powered or had too few variables to provide the desired clinical utility.