I. Introduction

Over time, repeated episodes of HS disease flares can lead to complications. Not everyone with HS is going to experience complications. For those that do, the complications can be limited to affecting the skin only or can cause internal problems in the body. Complications that cause internal problems are called systemic complications.

To prevent complications, early diagnosis and treatment of HS is of great importance.

It is easier to prevent complications than it is to treat existing complications.

This chapter discusses skin and systemic complications that people with HS may encounter.

II. Skin Complications

Tunnels. HS is a condition caused by an overactive immune system, as well as the abnormal plugging and rupture of hair follicles. These ruptured hair follicles are thought to be connected by tunnels formed under the skin. However, they can sometimes attach to the surface of the skin and drain foul-smelling fluid. In rare cases, tunnels will close and heal with medications that treat HS; however, most tunnels require surgical intervention. Your healthcare provider may assess the severity of your disease using a grading scale called “Hurley staging” which looks at the presence or absence of tunnels and scars, as well as the extent of disease involvement. Having tunnels signifies more advanced disease. Early diagnosis of HS and initiation of treatment may help prevent the formation of tunnels.

Scarring and Contractures. HS lesions can heal with discoloration and scarring. There are several types of scars that can form in people with HS, including:

• Depressed (indented) scars which can be darker or lighter than the surrounding skin.
• Thickened scars which are firm, raised, and can resemble a rope.
• Keloids, which are raised scars that extend past the area of the original wound or lesion. These scars can make the affected skin look abnormal and can also cause sensitivity and pain. Scarring can also lead to limb contractures. Limb contractures are areas of tightening or shortening of the skin that can limit movement, especially when occurring in the armpits or groin.The best way to prevent scars is to diagnose and treat HS early. If scars do develop, your healthcare provider may suggest steroid injections or lasers to help with the appearance of your scars if they are bothersome. Scars can also be surgically removed, but there is risk of new scars developing in their place.

Lymphedema. Lymphedema, a type of swelling, occurs when scars form near lymph nodes. Lymph nodes are part of the immune system. They help the body fight off infections by filtering and trapping viruses, bacteria, and other causes of infection. When scars form near lymph nodes, they can make it harder for fluid to drain from the lymph nodes, which causes swelling. A common area for lymphedema in HS patients is the groin. However, swelling can occur in any part of the body.

Depending on the location, lymphedema may be managed with compression treatments. Swelling in the groin is more difficult to compress and may require surgery or laser therapy to help remove the affected tissue and lymph nodes.

Fistulas. Long-term inflammation of HS can cause abnormal connections (or passageways) to develop between two organs that do not normally connect. These are called fistulas. The most common kind of fistula seen in HS patients is a tunnel that forms between the skin and the anus. This is more common in men than in women.

Symptoms of an anal fistula include persistent pain, swelling, and drainage of blood or pus involving the perianal skin. If a fistula is suspected, imaging tests such as magnetic resonance imaging (MRI) or computed tomography (CT) scans may be ordered to better evaluate the area. Fistulas usually require surgical treatment. However, treating HS inflammation early may help prevent fistula formation.

Skin Cancer: Squamous Cell Carcinoma. Squamous cell carcinoma (SCC) is a type of skin cancer that – in rare cases – can develop in areas of HS scarring and inflammation that have been around for a long time. SCC is a rare but serious complication of HS. It more commonly occurs in men. SCC associated with HS is usually found on the buttocks but can also be found in other areas, including the thighs, groin, and genital area.

There can be a delay in the diagnosis of SCC. This may be because HS lesions can sometimes look like SCC. If you have longstanding HS lesions, it is important to regularly see a dermatologist so that they can evaluate your skin lesions to screen for skin cancer. To diagnose SCC, your dermatologist may take a biopsy. If the diagnosis of SCC is made, your dermatologist will work with a team of other doctors to treat the skin cancer, including a surgeon who will perform a surgery to remove it. SCCs may come back even after removal, so it is important to continue regular skin examinations with your dermatologist.

III. Systemic Complications

Serious Infections and Sepsis. HS is not an infection. However, the areas affected by HS have the potential to become infected. This can result in serious infections of the skin, bone, and blood. Sepsis is an extremely rare but life-threatening complication that occurs when the body’s infection-fighting response damages its own tissues. Symptoms of sepsis include fever, confusion, a drop in blood pressure, and difficulty breathing. In rare cases, an infected HS lesion can lead to sepsis, especially as some medications used to treat HS can suppress the immune system, making a person more likely to develop an infection. It is important to seek care with a healthcare professional if you suspect you may have an infection.

Anemia. People with HS are more likely to have low levels of red blood cells, a condition known as anemia. These red blood cells are needed to carry oxygen to your body’s tissues. Having anemia can make you feel tired, weak, or short of breath. Anemia can develop when someone has a lot of chronic inflammation in their body, such as in people with HS. In these cases, treating the inflammation associated with HS may help improve the anemia.

Anemia can also be the result of having low levels of iron, which can occur from blood loss. People with HS may also have iron deficiency anemia. The cause of this is unknown, but may be related to blood loss from draining HS lesions, blood loss in women from periods, or bleeding from the gastrointestinal tract. A lab test can help determine the type of anemia that you have. If anemia is suspected, your primary care doctor can help with further work-up.

Amyloidosis. Many chronic inflammatory diseases, including HS, have the potential to cause amyloidosis. Amyloidosis is an extremely rare disease that occurs when a protein called amyloid builds up in your organs. This disrupts the normal function of your organs and, in severe cases, can cause organ failure. Although any organ can be affected, the kidneys are most often involved. Amyloidosis may improve with treatment of HS.