What Causes Hidradenitis Suppurativa
Doctors are still unsure of the causes of HS, but a malfunctioning immune system, genetics, hormones, unique anatomy of hair follicles, skin microbiome, and environmental triggers are all considered factors for HS.
HS is caused by the immune system generating too much inflammation. While we still need to learn more about HS, research has uncovered some information as to how HS can occur.
Your immune system is designed to be quiet and almost inactive when things are going fine. It is also designed to be on the lookout for threats and when something like bacteria starts to cause trouble, then the immune system’s cells and proteins get busy. After the problem is dealt with the immune system quiets down again.
For people with HS, their immune system is over-active, not defective. Sometimes people with HS think their immune system is under-active because they get what look like infections, but the HS lesions are inflammation, not an infection. Your immune system is overactive and causing inflammation that has too many of the cells and proteins that usually fight infection. The immune system doesn’t shut off when it should, causing lesions that last for a long time or keep coming and going.
Part of what causes HS is our genetics. Our genetics control the way our skin and immune system cells work. So, this is why HS can run in a family, but it’s not a guarantee that you will pass it on to any of your kids. The research says that for every three people with HS, one of them will have a family member with HS.
HS can be influenced by things we are exposed to, like smoking tobacco or friction, but these aren’t the only reasons why HS happens. We know that if you stop smoking tobacco then you decrease your risk of heart disease, stroke, and lung problems, but it’s not a guarantee that your HS will get better. The same is true for body weight. Research shows that if people are overweight and lose some weight, they will have better overall health, but it is not a guarantee that their HS will get better.
Bacteria are found on the skin of everyone, but for people with HS, the skin cells overreact and cause inflammation. The inflammation causes the skin cells to stick to the inside of the hair follicle.
It is the hair follicle, not the apocrine sweat glands; inflammation in the hair follicle skin cells causes them to block the opening. The skin cells build up and cause the hair follicle to get wider and weaker. The hair follicles may break open under the skin (rupture) and trigger even more massive skin inflammation, which may produce purulent discharge.
What is still unknown about HS?
For many years, HS was referred to as a disease of the apocrine glands. Apocrine glands are a type of sweat gland that appears in some of the areas where one can find HS spots – like the underarm and groin – but also in areas where HS spots are nearly unheard of – like the ear canal, eyelids, and nostril. Patients will also report having HS flare-ups in areas where there are no apocrine glands, like the abdomen, or thighs.
Science is not settled on this subject, but it is now thought that Hidradenitis Suppurativa is primarily a disease of the hair follicle and apocrine glands only become infected secondarily. Sources calling HS a disease of the sweat glands or apocrine glands are out of date.
Hidradenitis Suppurativa is one of the most difficult diseases in dermatology, in no small part because what works for one patient may not work for another. In fact, some treatments for HS are widely reported by some patients to make their condition worse!
Triggers also vary between individuals, also observing opposite reactions to some triggers. For example, many women report going into remission during pregnancy and others report it as being worse than ever. Some report being “cured” of their HS with menopause, and some women only begin to get symptoms with the onset of menopause. This is not understood, but experts theorize that there are many factors that contribute to HS and each factor may play a bigger or smaller role, depending entirely on the individual.
Some research has shown that certain groups are affected more than others. For example:
Sex: Women are 3x more likely to get HS than men.
Race: People who are Black or biracial are more likely to have HS than Caucasian people.
Genetics: HS can run in families. About 30% of people with HS have a family member who also has the disease.
Age: HS often starts after puberty - when you’re a teen or in your early 20’s - but it can also develop later in life in your 40’s or 50’s.
So, how do we measure the severity of HS?
Hidradenitis Suppurativa typically develops slowly over time. Development differs, however, from individual to individual. Most patients with HS (an estimated 2/3rds) will never develop past a mild stage. With others, it may escalate and become a debilitating disease. It is not known why.
The severity of an individual’s HS is commonly measured by Hurley Stages:
Stage I (“Mild”): Solitary or multiple isolated abscess formation without sinus tracts
Stage II (“Moderate”): Recurrent abscesses, single or multiple widely separated lesions, with beginning sinus tract formation (“tunnelling”)
Stage III (“Severe”): Diffuse or broad involvement across a regional area with multiple interconnected sinus tracts, significant scarring and persistent abscesses
The Hurley staging system was developed by Dr. H J Hurley, a dermatologist and surgeon looking to classify which patients would benefit from excision surgery in the management of their HS. Unfortunately, while this staging system is still widely in use today, it does not accurately measure activity (for example, once you have one sinus tract, you cannot go back down to Stage I without surgical excision). HS experts around the world, with direction and involvement from patients, are currently working together to develop a more accurate, reliable way to measure HS severity and activity.
Is HS a ‘new disease’ or is it just unknown?
Historically, HS has been considered a rare disorder, because it is difficult to accurately estimate the number of people living with HS; they conceal their condition, even from friends and close relatives. However, when all stages of the disease are considered, it is estimated that 1-4% of the population have Hidradenitis Suppurativa.
However, this is not a new disease.
HS was first depicted in 1833 by the French anatomist and surgeon Alfred-Armand-Louis-Marie Velpeau, which is where the name Velpeau's Disease originates. It was later investigated by French Surgeon, Aristide Auguste Stanislas Verneuil from 1854 to 1865, earning it the name Verneuil's Disease, and it was he who conducted the first clinical studies of HS.
Verneuil later renamed the disease Hidrosadenite Phlegmonous in 1864, which translates to the English Hidradenitis Suppurativa, meaning the inflammation of a sweat gland (Hidradenitis) containing or associated with pus (Suppurativa).
All information provided has been collected from the following organisations; https://hopeforhs.org, https://www.hs-foundation.org, and https://www.iahsn.org/. Please visit these amazing organisations for more information on HS.
