Hidradenitis suppurativa

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

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 signs and symptoms of hidradenitis suppurativa appear after puberty, usually in a person's teens or twenties.

The recurrent nodules and abscesses cause chronic pain and can lead to self-consciousness, social isolation, and depression. Less common complications of hidradenitis suppurativa include severe infections, restricted movement caused by a buildup of scar tissue (fibrosis), and a type of skin cancer called squamous cell carcinoma.

Hidradenitis suppurativa was once thought to be a rare condition because only the most severe cases were reported. However, recent studies have shown that the condition affects about 1 in 100 people when milder cases are also considered. For reasons that are unclear, women are about three times more likely than men to develop the condition.

The cause of hidradenitis suppurativa is unknown, although it probably results from a combination of genetic and environmental factors. Originally, researchers believed that the disorder was caused by the blockage of specialized sweat glands called apocrine glands. However, recent studies have shown that the condition actually begins with a blockage of hair follicles in areas of the body that also contain a high concentration of apocrine glands (such as the armpits and groin). The blocked hair follicles trap bacteria, leading to infection and inflammation. It remains unclear what initially causes the follicles to become blocked and why the nodules tend to recur.

Researchers have studied many possible risk factors for hidradenitis suppurativa. Obesity and smoking both appear to increase the risk of the disorder, and obesity is also associated with increased severity of signs and symptoms in affected individuals. Studies suggest that neither abnormal immune system function nor hormonal factors play a significant role in causing the disease. Other factors that were mistakenly thought to be associated with this condition include poor hygiene, the use of underarm deodorants and antiperspirants, and shaving or the use of depilatory products to remove hair.

Genetic factors clearly play a role in causing hidradenitis suppurativa. In one large family, researchers determined that the condition was related to a gene on chromosome 1 (although they were not able to identify the specific gene). Researchers are looking for additional genetic factors that are associated with hidradenitis suppurativa.

Hidradenitis suppurativa has been reported to run in families. Studies have found that 30 to 40 percent of affected individuals have at least one family member with the disorder, although this finding may be an underestimate because affected individuals do not always tell their family members that they have the condition.

In some families, hidradenitis suppurativa appears to have an autosomal dominant pattern of inheritance, which means one copy of an altered gene in each cell is sufficient to cause the disorder. However, the specific gene or genes have not been identified.