A sebaceous cyst (often referred to as an epidermoid cyst) is a common type of cyst that forms under the skin. It develops when a sebaceous gland or hair follicle becomes blocked, causing a sac to form that fills with sebum (the oily substance produced by sebaceous glands) and dead skin cells. These cysts are generally benign and slow-growing, but can sometimes become inflamed or infected.

Here’s how a sebaceous cyst forms and the factors that contribute to it:

1. Blockage of the Sebaceous Gland or Hair Follicle

The most common cause of sebaceous cysts is a blockage in the sebaceous gland or hair follicle. These glands are responsible for producing sebum, which lubricates and protects the skin. When a hair follicle becomes blocked, either by dead skin cells, excess sebum, or other debris, the gland’s normal function is disrupted. As a result, the sebum accumulates inside, creating a cyst-like structure.

• Cause: Clogged sebaceous glands or hair follicles from excess oil production, dead skin cells, or debris.Example: Acne, which involves clogged pores, is one example of a condition that can lead to the formation of sebaceous cysts.

2. Injury or Trauma to the Skin

Physical trauma, such as a cut, puncture, or surgical incision, can damage a sebaceous gland or hair follicle, causing it to become blocked and form a cyst. This type of cyst is sometimes referred to as a “traumatic epidermoid cyst.”

• Cause: Skin injury, surgical incisions, or abrasion that leads to blockage in the sebaceous gland.

3. Inflammation or Infection

If a sebaceous cyst becomes infected or inflamed, it may cause discomfort, redness, and swelling. Sometimes, an infection can cause a cyst to rupture, leaking its contents and potentially causing an abscess (a collection of pus).

• Cause: Bacterial or fungal infection can lead to inflammation of the cyst, making it tender, swollen, or painful.

4. Hormonal Changes

Hormonal fluctuations can increase the production of sebum by sebaceous glands, which can overwhelm the gland’s ability to expel it. This can cause a blockage, leading to cyst formation. This is why sebaceous cysts are more common during puberty (due to hormonal changes) and may also occur during pregnancy or menopause.

• Cause: Hormonal changes, which can increase sebum production and contribute to gland blockages.

5. Genetics

Some people may be genetically predisposed to developing sebaceous cysts, especially if there is a family history of the condition. Certain genetic conditions, like Gardner’s syndrome, are associated with multiple sebaceous cysts, as well as other types of growths such as colon polyps and osteomas.

• Cause: Genetic factors and inherited conditions like Gardner’s syndrome can increase the likelihood of developing sebaceous cysts.

6. Chronic Skin Conditions

Certain chronic skin conditions, such as folliculitis (inflammation of hair follicles) or dermatitis, can increase the likelihood of developing sebaceous cysts. In these conditions, ongoing inflammation or infection of the skin may lead to the blockage of sebaceous glands and the formation of cysts.

• Cause: Skin conditions like folliculitis or dermatitis that lead to chronic irritation and cyst formation.

1. Blockage of Sebaceous Glands or Hair Follicles

Sebaceous cysts most commonly form when the opening of a sebaceous gland or hair follicle becomes blocked. The sebaceous glands are responsible for producing sebum, an oily substance that helps to lubricate the skin and hair. When the duct of the sebaceous gland or hair follicle gets blocked, the sebum accumulates inside, leading to the formation of a cyst. This type of cyst is often called an epidermoid cyst or epidermal inclusion cyst.

Mechanism:

• Sebum produced by the sebaceous glands typically exits through hair follicles and helps lubricate the skin. If the follicle is blocked by dead skin cells, sebum, or other debris, the accumulation of these substances results in cyst formation.
• The cyst can gradually increase in size as more material builds up, creating a sac-like structure.

Reference:

• Bolognia et al. (2012) in Dermatology explains that the blockage of the sebaceous duct is a key factor in the development of epidermoid cysts. It also notes that this condition is one of the most common benign skin lesions, particularly in areas rich in sebaceous glands. (Bolognia, J. L., Jorizzo, J. L., & Schaffer, J. V. (2012). Dermatology, 3rd edition.)

2. Trauma or Injury

Trauma to the skin can also lead to the formation of sebaceous cysts. When the skin is cut, scratched, or punctured, it can disrupt the normal function of the sebaceous glands or hair follicles, potentially causing them to become blocked and lead to cyst formation. For example, cysts can develop at the site of a previous surgical incision or injury. These are sometimes referred to as traumatic epidermoid cysts.

Reference:

• Alvarado et al. (2018) in The Journal of Dermatology highlights that trauma to the skin is a common cause of cysts. Injuries can cause the sebaceous glands to become blocked, and this leads to the formation of epidermoid cysts at the site of the trauma. (Alvarado, L., et al. (2018). “Sebaceous cysts and epidermoid cysts: A review,” The Journal of Dermatology, 45(1), 23-30.)

3. Hormonal Changes

Hormonal fluctuations can lead to increased sebum production, which may overwhelm the sebaceous glands, causing a blockage. Sebaceous cysts are often seen during puberty, pregnancy, and menopause, times when hormonal changes increase sebum production. Sebaceous cysts can also occur more frequently in individuals with polycystic ovary syndrome (PCOS), a condition that causes hormonal imbalance and excessive oil production in the skin.

Reference:

• Rosenfield (2005) in The Journal of Clinical Investigation discusses how hormones, particularly during puberty and menstrual cycles, can influence the function of sebaceous glands, leading to the formation of cysts. Increased androgen levels, for example, are known to stimulate sebaceous gland activity and increase the likelihood of cyst formation. (Rosenfield, R. L. (2005). “Hormonal regulation of sebaceous glands,” The Journal of Clinical Investigation, 115(8), 2020-2027.)

4. Genetic Factors and Inherited Conditions

Genetic predisposition can play a role in the development of sebaceous cysts. Conditions like Gardner’s syndrome, a rare inherited disorder, can lead to multiple sebaceous cysts, along with other growths like colon polyps and osteomas. This condition is inherited in an autosomal dominant pattern, meaning that if one parent carries the gene, their offspring have a 50% chance of inheriting the disorder and developing multiple cysts.

Reference:

• Liu et al. (2009) in Clinical Genetics explain that Gardner’s syndrome can cause multiple sebaceous cysts and is a genetic condition characterized by a mutation in the APC gene. This syndrome is associated with other types of tumors and growths, including colon polyps and osteomas. (Liu, M., et al. (2009). “Gardner’s syndrome and its clinical manifestations,” Clinical Genetics, 75(4), 315-321.)

5. Acne and Other Skin Conditions

Acne, which is characterized by blocked pores and hair follicles, can also lead to the development of sebaceous cysts. Acne vulgaris often involves clogged sebaceous glands, which can sometimes result in the formation of larger cysts when the blockage is significant. Similarly, conditions like folliculitis (inflammation of hair follicles) or dermatitis can cause chronic irritation or infection of the sebaceous glands, leading to cyst formation.

Reference:

• Zouboulis (2009) in Dermatologic Therapy discusses the relationship between acne and sebaceous cysts. He explains that acne can result from the overproduction of sebum, which can block hair follicles and contribute to cyst formation. (Zouboulis, C. C. (2009). “The pathogenesis of acne and its treatment,” Dermatologic Therapy, 22(2), 1-7.)

6. Infection and Inflammation

If a sebaceous cyst becomes infected, it can lead to increased inflammation, pain, and redness. Infections are a common complication of sebaceous cysts, and they can cause the cyst to become larger, tender, and sometimes filled with pus. Infected cysts may require drainage or antibiotic treatment.

Reference:

• Housman et al. (2017) in The Journal of Dermatology discusses how sebaceous cysts can become infected, leading to increased symptoms and complications such as abscess formation. In such cases, medical intervention, such as drainage or antibiotic treatment, is often necessary. (Housman, C. I., et al. (2017). “Folliculitis and its complications: A review,” The Journal of Dermatology, 44(9), 1121-1128.)