Glossary of Hidradenitis Suppurativa Terms

Reviewed by: HU Medical Review Board | Last reviewed: December 2020


Actinic keratoses

Scaly skin spots that show some abnormality caused by chronic sun exposure.1


A class of steroid hormone responsible for the development of male characteristics.1


Refers to medication taken by women to cancel out the effect of male sex hormones, such as testosterone.2

Apocrine glands

Scent glands mostly found in armpits and groin, which become active after puberty. Apocrine sweat is oily, thick, and odorless; the smell comes from bacterial decomposition.1

Autoimmune disorder

Auto means self; so an autoimmune disorder is a condition in which the immune system cannot recognize foreign invaders (viruses, bacteria, fungi) from itself. The immune system attacks and destroys healthy tissue by mistake.3

Axial spondyloarthritis

A type of arthritis. It mostly causes pain and swelling in the spine and the joints that connect the bottom of the spine to the pelvis (sacroiliac joint). Other joints can be affected as well. It is a systemic disease, which means it may affect other body parts and organs.4



Blocked hair follicles in the skin. Skin cell debris combines with oil (sebum) to plug the follicle. A comedo can be open (blackhead) or closed by skin (whitehead).1,2


Deformity caused by permanent shortening of tissues across joints.1


Steroid hormones made in the adrenal gland or in a lab. They are used as a topical (applied on the skin), inhaled, or systemic (medicines that affect the whole body) drug. Corticosteroids control inflammation.1,5



A doctor or surgeon who specializes in treating conditions and diseases of the skin, hair, and nails.1


The fibrous layer of the skin just below the epidermis (outer layer). This layer contains blood vessels, nerves, hair follicles, sweat and scent glands, and other structures.1


A tissue-saving technique, through wich the “roof” of an abscess, cyst, or sinus tract is removed by electrosurgery.6



A narrow pit in the skin within which a hair grows.1

Follicular occlusion tetrad

The group of four diseases in which hair follicles become blocked with keratin (the protein that makes up hair and nails) and then rupture, resulting in inflammatory skin disease. These conditions usually exist at the same time. They may be severe and hard to treat.2



A male pattern of secondary or post-pubertal hair growth occurring in women. It appears in the mustache and beard areas at puberty. Hirsute women may also develop thicker, longer hair than is usual on their limbs and torso.2

Hydrocolloid bandage

A bandage made of a gel. It molds to the sore and promotes healing and skin growth. These dressings can stay on for several days at a time.7



Drugs that reduce activity of the immune system. Immunosuppressants are used to prevent rejection of a transplanted organ and to treat autoimmune diseases and allergies. They also reduce the body’s ability to fight infection and other diseases.8


A tissue response to injury or disease. In the skin, it causes redness, swelling, heat, pain, or itch.1



The protein that makes up the outer layer of the skin, hair, and nails.1


Any scaly skin lesion.1



A broad term, including wounds, sores, ulcers, tumors, cataracts, and any other tissue damage. Lesions range from the skin sores associated with eczema to the changes in lung tissue that occur in tuberculosis.9


Metabolic syndrome

The presence of 3 or more of these conditions: large waist size, high triglycerides, low levels of HDL (“good”) cholesterol, high blood pressure, and high blood sugar levels. Metabolic syndrome increases the risk of heart disease and type 2 diabetes.10


Pilonidal sinus

A small hole or tunnel in the skin at the top of the buttocks, where they divide (the cleft).11

Polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is characterized by menstrual irregularities, hirsutism (male-like hairiness in women), obesity, and metabolic syndrome, resulting from abnormalities in the metabolism of androgens* and estrogen and in the control of androgen production.2



Vitamin A-based medications. They are not as effective for treating HS as they are for treating acne, but they may help some people. They must be used with caution and cannot be taken by women who are pregnant.12



Sebum is an oily substance produced by sebaceous glands in the skin. Sebum helps condition the hair and surrounding skin.13


A dead-ended (blind-ended) tunnel or cavity connecting to the skin or mucosal surface. A sinus may be congenital (present from birth) or acquired.1

Squamous cell carcinoma

Skin cancer. The second most common cancer in the United States. Squamous cell cancer affects the epidermis, the top layer of skin. Its common precursors are actinic keratoses.14


Terminal hair

The thick, long hair that normally occurs on the scalp and, after puberty, in the armpits, beard, and pubic area.1

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