The symptoms of hidradenitis suppurativa (HS, also known as acne inversa) may appear similar to symptoms of other conditions. Pilonidal cysts, in particular — pockets of skin cells and hair that typically develop at the tailbone — may be confused with HS lesions.

Despite their similarities, HS and pilonidal cysts are distinct conditions with their own causes and treatments. Although the differences between the two should be clear to a doctor or dermatologist, it may help you to understand the differences between the symptoms, causes, and treatments of pilonidal cysts and HS.

What Are Pilonidal Cysts?

A pilonidal cyst is not actually a cyst, but it’s called that for lack of a better term. Instead, a pilonidal cyst is an abnormal pocket in the skin, usually located around the tailbone or in the top third of the cleft of the buttocks.

Left alone, these pockets are not problematic. However, hair can puncture the skin and then grow into and fill the space, along with dead skin cells. If this pocket becomes infected, it creates a pilonidal abscess, which can be extremely painful.

The Relationship Between HS and Pilonidal Cysts

Researchers are not sure exactly how HS and pilonidal cysts are related, but there does seem to be a connection between the two. While the conditions do not always share the same features, the conditions share enough that researchers think pilonidal cysts might be one type of HS. The cysts might also be how HS manifests in the tailbone and upper buttocks region.

Some people are diagnosed with both HS and pilonidal cysts, either at the same time or at different points in their lives. Other people only ever develop one or the other condition.

HS and pilonidal cysts may have similar underlying causes. More research is necessary to understand how the two conditions are likely connected and to explain why they sometimes appear together.

Symptoms of HS and Pilonidal Cysts

Both HS and pilonidal cysts can involve hard lumps under the skin that can become infected and painful. Such infections can require medical treatment, even surgery.

HS can occur anywhere where skin rubs together and where there are a lot of sweat glands, like in the armpits, inner thighs, or groin. Pilonidal cysts develop almost exclusively near the tailbone or in the upper part of the cleft between the buttocks.

HS may first appear as blackheads (bumps with dark-colored centers) or as pea-sized lumps under the skin. These bumps don’t go away for weeks and may feel painful and itchy. Over time, they may get bigger and begin to ooze. If left untreated, these bumps may form tunnels under the skin (sinus tracts) that continually ooze.

People may not notice pilonidal cysts before the cysts become infected. If the cysts are noticeable, they will simply feel like lumps under the skin. Symptoms of infection include swelling, pain, discolored skin around the infected area, and oozing.

In some cases, the pocket of a pilonidal cyst can connect to other cysts, creating narrow tracts of dead cells, hair, and infection under the skin. These tracts are known as pilonidal sinus tracts. This symptom may lead a person to believe they have HS, as the development of sinus tracts is characteristic of HS.

Causes and Risk Factors of HS and Pilonidal Cysts

No one knows exactly what causes pilonidal cysts to form, though the immediate cause involves hairs that pass the skin barrier. The cysts can be exacerbated by wearing tight clothing, having long periods of inactivity (like sitting in front of a computer for work), having a lot of body hair, or having coarse or stiff body hair.

Risk factors for pilonidal cysts include:

• Younger age (usually in the 20s)
• Obesity
• Being male
• Inactivity

HS occurs when hair follicles (the small spaces around the roots of the hairs) become clogged. Clogging often happens when certain types of cells grow too quickly and prevent the body’s naturally occurring oils from escaping. As with pilonidal cysts, researchers aren’t sure exactly why HS occurs, though research is ongoing. What is known is that HS is not caused by poor hygiene or sexually transmitted infections.

People at risk of developing HS include:

• People with a family history of HS
• People who smoke
• Those who are overweight or obese
• Those who have been diagnosed with certain other conditions, including arthritis, diabetes, inflammatory bowel disease, and metabolic syndrome
• Women in their 20s and 30s
• African American people

Diagnosing HS and Pilonidal Cysts

The diagnostic process for pilonidal cysts and HS is often similar, particularly at the onset of the conditions. If your doctor suspects you might have a pilonidal cyst or HS, they will likely take a comprehensive medical history. They will focus specifically on your or your family’s skin diagnoses and other diagnoses often related to HS.

The doctor will then typically perform a thorough examination of the affected areas of skin, noting where your breakouts are located. The doctor may ask when your symptoms first appeared, how long the symptoms usually last or have lasted, and whether they are constant or tend to disappear then reappear.

Your doctor may also perform a dermoscopy, which is a microscopic examination of the affected skin cells. If you have sores, cysts, nodules, pimples, or lesions that are draining fluid or pus, the doctor may take a sample of this fluid for further examination.

Finally, your doctor may ask for a blood test, especially if the doctor suspects HS. Certain markers in your blood can indicate HS, as opposed to a pilonidal cyst.

Treating HS and Pilonidal Cysts

Some treatment options for pilonidal cysts and HS overlap. For instance, both may be treated with oral and topical antibiotics. Antibiotics can reduce inflammation of the skin and resolve infection, not heal the underlying condition.

Both conditions may also be treated with other oral medications or creams to fight inflammation, including nonsteroidal anti-inflammatory drugs and corticosteroids.

Pilonidal cysts that develop into abscesses will typically need to be drained. If follow-up appointments show that draining did not resolve the issue, surgical treatment (an excision) may be necessary to clear out the entire area. After that, laser hair removal may be needed to reduce the number of hairs growing in the area and prevent further issues. Phenol injections may also help reduce the incidence of cysts and abscesses.

HS may require treatment with biologic medications such as Humira (adalimumab). Biologics are designed to lower the body’s inflammation levels. HS related to hormones may be controlled by taking hormonal birth control, while retinoids have also proven helpful for some people. In some cases, HS abscesses may need to be drained. HS lesions may also be treated with a laser to clear them of fluid.

Find Your Team

On myHSteam, the social network for people with hidradenitis suppurativa and their loved ones, more than 23,000 members come together to ask questions, give advice, and share their experiences with others who understand life with HS.

Have you dealt with pilonidal cysts? Share your thoughts in the comments below, or by posting on myHSteam.