The exact cause of hidradenitis suppurativa is not known, although there are a number of theories that attempt to explain the condition. It is, however, clear that the disease is not communicable and cannot be passed between people. Additionally, poor hygiene is not thought to be involved in the pathophysiology.
The most prominent theory to explain the cause behind hidradenitis suppurativa is a blockage of the hair follicles in the skin, known as follicular occlusion. This may be as a result of sweat or sebum from the sebaceous glands becoming trapped in the follicle, forming a plug and obstructing the normal movement through the follicle.
As a result of this, the inflammatory pathways can be activated and result in perifolliculitis (inflammation around the follicle).
In some cases, the abscess can rupture and allow the entry of bacteria into the hair follicle. The warm, moist environment promotes the growth of many bacteria and can lead to a secondary bacterial infection and the development of pus.
Some medical researchers believe that the sweat glands themselves develop abnormally to cause the condition. It is thought that the sweat and sebum can’t move through the follicle to the surface of the skin as a result of structural errors in the formation of the follicle.
It has been noted that several members within one family are often affected be hidradenitis suppurativa. It is estimated that up to one third of patients with the condition have at least one known family member that suffer the condition.
An abnormality in the PSTPIP1 gene has been noted in several patients. This gene is linked to PAPA syndrome, along with other related conditions: pyoderma gangrenosum, acne and pyogenic arthritis.
The most common age for symptoms of hidradenitis suppurativa to present and the condition to be diagnosed is shortly after puberty, at around twenty years old. The condition is also rare before puberty or after menopause. This suggests that hormones may be involved in causing the condition.
Sex hormones such as androgen and oestrogen affect the function of apocrine sweat glands. It is agreed the androgen stimulates the sweat glands and oestrogen suppresses them, although the exact interplay of these hormones is still under discussion.
Administration of progesterone as a stand-alone contraceptive has been associated with worsening of hidradenitis suppurativa symptoms, suggesting the hormone is involved in the pathophysiology of the condition.
Some disorders of the endocrine system have also been linked to hidradenitis suppurativa. These include:
- Polycystic ovaries
There are several factors that are linked to an increased risk of developing hidradenitis suppurativa, although it is unclear if they cause the condition. These include:
- Gender: women are three times more likely than men to be affected
- Age: individuals between the ages of 20 and 40 years are at greatest risk
- Smokers: mechanism unclear but a history of smoking appears to increase risk
- Obesity: individuals that have excess weight tend to have more folds in the skin, where lesions tend to appear
- Medications: some medications (e.g. lithium, POP contraceptive) may increase risk
Additionally, there are some other health conditions that are linked to hidradenitis suppurativa and may be involved in causing the condition.
For example, Crohn’s disease appears to stimulate the progression of hidradenitis suppurativa. Additionally, follicular occlusion syndrome is a syndrome that includes hidradenitis suppurativa in association with acne, conglobate, dissecting cellulitis and pilonidal sinus.