The efficacy of laser hair removal therapy in patients with mild to moderate HS, a randomized controlled trial.

Hidradenitis suppurativa (HS) is a chronic, recurrent and debilitating skin
disorder, characterized by painful inflamed nodules, abscesses and tunnels,
mainly in skin folds, such as the axillae, inguinal region and gluteal area.
The primary cause of HS is an occlusion of the hair follicle. Several
etiological factors (genetics, lifestyle, hormonal status and dysbiotic
microbiota), induce immune activation of the outer root sheet keratinocytes,
leading to acantohosis and hyperkeratosis of the infundibulum. This results in
an occlusion of the terminal hair follicle, with subsequent dilatation and cyst
formation. When rupture of the hair follicle occurs, an inflammatory response
ensues, resulting in the typical clinical lesions of HS. HS severity can be
described using a classification system, such as the international hidradenitis
suppurativa severity score system (IHS4). Previous studies showed that
patients with mild to moderate HS are 95,3% of the total HS population.
Although most patients have mild to moderate disease, clinical trials are
focused on moderate and severe HS. This development has been noticed by patient
advocate groups and they requested to an additional focus on milder cases of
HS, to create more treatment options for this group.

Previous studies showed significant results in favor of laser hair removal in
patient with HS compared to just topical therapy. Hair grows in three phases;
first, there is active growth, called the anagen phase, Second, a hair goes in
regression, called the catagen phase and third, at last a hair goes into a
resting phase, called the telogen phase. This cyclic pattern of hair growth is
significant because only hairs in the anagen phase are sensitive to the effect
of hair laser therapy. Therefore, a patient needs several treatments to treat
all hair follicles.

Considering the fact that HS arises in the hair follicle, we hypothesized that
permanent removal of the hair could prevent further development of HS.
Furthermore, in our experience, there is a high demand for laser hair removal
therapy under patients with HS, but fundamental research to validate this has
not been conducted yet.

The primary objective of this study is to assess whether laser hair removal
therapy improves the course and severity of mild to moderate HS, as assessed by
the difference in IHS4 between groups over time between month 7 to month 12.

This study is a RCT with a duration of 12 months, which is divided into 2
periods of 6 months.

The RCT consist of two periods of 6 months. From month 1 to month 6, the
intervention group will undergo six monthly laser hair removal treatments in
the axillae or inguinal area combined with clindamycin 1% lotion if needed,
while the control group uses only clindamycin 1% lotion if needed. From month 6
to 12, there is a observational follow up of six months. During this period,
both groups will use clindamycin 1% lotion if needed.

Patients will visit the out-patient clinic every month for a period of 12
months. Every visit a doctor will check the skin for HS lesions and the patient
will fill out some questionnaires. The patients in the intervention group will
undergo 6 hair laser removal treatments. This is a non-invasive treatment with
minimal side effects, which mostly disappear within 24 hours. Prevention of
side effects will be achieved by using correct settings of the laser device and
the use of cooling and a narcotic creme. Compared to standard care, the amount
of hospital visit is larger, but considering the high demand for laser hair
removal therapy among patients, we think that a lot of patients want to
participate.
Clindamycin 1% lotion if needed is standard of care and described in the
guidelines of HS. Patients could experience some dry skin when using
clindamycin 1% lotion.