Hidradenitis suppurativa, also known as acne inversa, is a chronic skin disease characterized by recurrent boil-like lumps (nodules) under the skin. The nodules become inflamed and painful. They tend to break open (rupture), causing abscesses that drain fluid and pus. As the abscesses heal, they produce significant scarring of the skin.

The signs and symptoms of hidradenitis suppurativa typically appear after puberty, usually in a person's teens or twenties, although they can begin earlier in puberty, particularly in affected females. Nodules are most likely to form in the armpits and groin. They may also develop around the anus, on the buttocks, or under the breasts. In some cases, nodules appear in other areas, such as the nape of the neck, waist, and inner thighs.

The recurrent nodules and abscesses cause chronic pain and can lead to self-consciousness, social isolation, and depression. Rarely, long-term (chronic) abscesses on the buttocks can develop into a type of skin cancer called squamous cell carcinoma.

The skin lesions of hidradenitis suppurativa (HS) are due to the abnormal blockage of hair follicles. This leads to an immune response which causes swelling, itching, and redness (inflammation). The inflamed lesions in the hair follicles fill with pus and blood causing the lesions to eventually burst open.

The underlying cause of HS is not known in most cases. Genetic, auto-inflammatory, hormonal, and environmental factors may be involved. Obesity and smoking may play a role in the severity of the disease. Thirty to forty percent of people with HS have at least one other family member with HS. Some cases of HS have been found to result from changes (mutations) in the NCSTN, PSEN1, or PSENEN gene. More studies are needed to determine whether other genes might be involved.

In some families, an increased risk (predisposition) to develop hidradenitis suppurativa (HS) is inherited in an autosomal dominant pattern. Like most genes, the NCSTN, PSEN1, and PSENEN genes come in pairs. Autosomal dominant means a person only needs a mutation in one copy of one of these genes to have an increased risk to develop HS.

Each child of an individual with an autosomal dominant condition has a 50% or 1 in 2 chance of inheriting the mutation and the condition. Offspring who inherit the mutation will have the condition, although they could be more or less severely affected than their parent. Sometimes a person may have a gene mutation for an autosomal dominant condition and show no signs or symptoms of the condition.

A person with HS has a 50% (1 in 2) chance to pass a mutation increasing the risk of developing HS on to each of his or her children. In addition to inheriting the mutation, exposure to other factors in the environment, hormonal changes, and/or the response of the immune system appear to also be needed for person to develop HS. Many people with HS have no family history of the disease.

The symptoms of hidradenitis suppurativa (HS) include:

• Small pitted areas of skin containing blackheads
• Painful, red, bumps or lesions that enlarge, break open, and drain pus that may have an unpleasant odor
• Leaking bumps or sores that heal very slowly, recur over time, and can lead to scarring and tunnels under the skin (called sinus tracts)

Symptoms occur in places where skin rubs together such as the armpits, groin, buttocks, and under the breasts.

HS most often starts after puberty, lasts for years, and gets worse over time. HS is described as either mild, moderate, or severe. In the mild stage, people with HS have a single or a few lesions in one area of the skin. In this stage, the disease is often misdiagnosed. HS will eventually progress to moderate disease which includes repeated cycles of lesions that enlarge and break open. The lesions form in more than one body area where skin rubs together. In severe HS, people may have widespread lesions, scarring, and chronic pain that may make it hard to move.

There is not one specific test for diagnosing hidradenitis suppurativa (HS), and the disease is often misdiagnosed in the early stages. The diagnosis of this disease is made based on the identifying the typical skin lesions in areas of skin folds, a history of having the lesions more than one time, and a history of painful lesions that discharge pus.

Testing Resources

• The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.

There is no one reliably effective treatment for hidradenitis suppurativa (HS). For mild HS, topical antibiotics, injected corticosteroids, or anti-inflammatory pills may be used. Oral antibiotics may be used to help prevent new lesions. For moderate disease, people may be treated with oral antibiotics, oral retinoids such as isotretinoin, hormonal therapy, and/or surgery. For severe disease, medications that block TNF-alpha proteins which are involved in the inflammation process are used. Some of the these TNF-alpha inhibitors include adalimumab and infliximab. Adalimumab has been approved by the FDA for treatment of HS. In addition, other inflammatory system suppressants and strong antibiotics have been used, along with surgery for very difficult to treat areas. Other types of therapy are still being researched.European guidelines for the management of HS have been published.

Losing weight and quitting smoking can help with the symptoms of HS. In addition, people with HS are advised to wear loose fitting clothing and avoid skin abrasions. People with HS should also be monitored for signs of depression and anxiety.

FDA-Approved Treatments

The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition.

• Adalimumab(Brand name: Humira) - Manufactured by AbbVie Inc.
  FDA-approved indication: October 2018, adalimunab (Humira) received expanded approval for the treatment of moderate to severe hidradenitis suppurativa (HS) to include patients 12 years and up. It was originally approved for adults with moderate to severe HS in September 2015.