The occurrence of pruritis in patients with hidradenitis suppurativa:
a cross-sectional study

Hidradenitis suppurativa (HS), also known as acne inversa, is a chronic,
recurrent, inflammatory skin disease. The disease mostly develops after puberty
and is characterized by painful, inflammatory nodules and abscesses mainly
located at the axillae and groin. The disease is common, with an estimated
prevalence rate between 1 and 4%. The pathogenesis of HS is still not fully
understood, but infundibular hyperkeratosis, causing follicular occlusion is
thought to be the primary event followed by rupture with an inflammatory
response.
The key physical symptoms of HS are pain due to inflammation of the skin and
purulent foul-smelling discharge in case of abscesses and fistulas. In general,
pruritis is a prominent symptom of many dermatological (inflammatory) diseases,
including atopic dermatitis, psoriasis, urticaria and postburn healing.
Pruritis is a multidimensional phenomenon with sensory discriminative,
cognitive, evaluative and motivational components. Pruritis has many
similarities to pain. Both are unpleasant sensory experiences, but the
behavioral response patterns differ - pain elicits a reflex withdrawal, whereas
itch leads to a scratch reflex. In addition to the other characteristics of HS,
chronic or recurrent pruritus can contribute to a significant reduction in
quality of life.
In psoriasis pruritis is a common symptom and a prevalence rate of 30% to 90%
is described. To date, the occurrence of pruritis in HS has not been widely
examined. Since the prevalence of pruritis in HS is unknown, we will conduct a
questionnaire-based survey according to a cross-sectional approach.

Hypothesis
We hypothesize a prevalence of 50-75% in patients with hidradenitis
suppurativa, depending on HS disease severity and number of affected anatomical
regions.

Primary:
To determine the prevalence of pruritis in patients with hidradenitis
suppurativa.

Secondary:
- to evaluate pruritis severity and its effect on three elements of daily
activities;
- to evaluate differences in extensiveness of HS in relation to pruritis
severity and the number of anatomical regions affected by HS.
- to screen the serum levels of pruritis markers tryptase, hemoglobin, ureum
and bilirubin in a subset of patients.

Cross-sectional study.

Invasive for a subset of approximately 30 patients (Nature and extent of the
burden and risks associated with participation, benefit and group relatedness).

Patients will be recruited during routine clinical care. All patients will be
asked to fill out the standardized *5D Pruritis Scale* questionnaire once. HS
patients with a VAS >7 for pruritis in the last 24 hours will be asked to give
permission for a one-time collection of blood samples (3 tubes) by
venipuncture. For this selected group of approximately 30 subjects in the HS
group there are minor additional risks associated with participation as a
result of the venipuncture. The very minimal risks of venipuncture include
excessive bleeding, fainting or feeling light-headed, hematoma or blood
accumulating under the skin, infection (a slight risk any time the skin barrier
is broken) and multiple punctures to locate veins. There is no extra visit due
to the study for all participants. Clinical (outcome) parameters will be
collected during routine care and derived from medical charts. All personal
data of the participating patients will be replaced by a code. The patient*s
data will be added in a database using this code. Further research will be done
with this anonymized database. All research data will be handled in accordance
with the Dutch Data Protection Act and the privacy regulations of the Erasmus
MC. No data that can be traced back to the participating patients will be used
in study documents, reports or in publications of this research.