Steatocystoma multiplex is a rare skin condition characterized by the development of multiple cysts filled with sebum. These cysts arise from the sebaceous glands, which are the tiny oil-producing glands in our skin that are attached to hair follicles. The job of the sebaceous gland is to produce an oily, waxy substance called sebum, which travels up a small tube called a sebaceous duct to lubricate the hair and skin.

In steatocystoma multiplex, there is a malformation of this tiny duct. A helpful analogy is to think of each of your hair follicles as having a tiny, attached oil dispenser (a sebaceous gland) with a narrow nozzle leading to the skin’s surface. In steatocystoma multiplex, the nozzle of this dispenser is faulty or blocked. The oil gland keeps producing oil, but it has nowhere to go. The oil backs up and collects in a small, balloon-like sac under the skin. This trapped, oily material is a steatocystoma.

It is important to differentiate between steatocystoma multiplex, where numerous cysts appear due to a genetic trait, and steatocystoma simplex, which is the term for a single, isolated steatocystoma that can appear in anyone with no family history.

In my experience, this condition is often misidentified as acne or lipomas. However, the smooth, rubbery feel and distribution of these cysts offer important clues for accurate diagnosis.

Steatocystoma multiplex is caused by a genetic mutation that affects the structural integrity of the sebaceous gland duct. The most well-established cause is a mutation in the Keratin 17 (KRT17) gene (NORD, 2021).

The KRT17 gene contains the instructions for making a specific type of keratin protein. Keratins are the fibrous structural proteins that make up our hair, nails, and, critically, provide strength and structure to the cells that line the ducts of skin glands. A mutation in this gene leads to a faulty keratin protein, which in turn results in a weak and malformed sebaceous duct that is prone to blockage and cyst formation.

I’ve often seen steatocystoma multiplex appear around adolescence, which aligns with hormonal changes and increased oil production especially in genetically predisposed individuals.

Steatocystoma multiplex is a genetic disorder. It is not contagious and cannot be acquired through contact or lifestyle. The way it is passed down can vary.

• Autosomal Dominant Inheritance: This is the most common pattern, seen in about 75% of familial cases. In this form, an individual only needs to inherit one copy of the mutated KRT17 gene from one affected parent to develop the condition. An affected parent has a 50% chance of passing the gene on to each of their children.
• Sporadic Cases: In about 25% of cases, the condition appears due to a de novo (new) mutation in the KRT17 gene. This means the mutation occurs spontaneously in an individual with no prior family history of the disorder.

The condition affects both males and females equally and is seen in all racial and ethnic groups.

Most patients are surprised to learn it’s genetic. I usually explain that it’s more about how their skin is programmed to develop especially when oily glands are involved, not something they did or didn’t do.

The primary and often only sign of steatocystoma multiplex is the appearance of the cysts themselves. The condition typically begins to manifest during adolescence or early adulthood, a time when hormonal changes increase the activity of the sebaceous glands.

The key features of the cysts include:

• Appearance: They are small, soft-to-firm, mobile bumps (papules or nodules) under the skin.
• Size: They typically range from a few millimeters to 2-3 centimeters in diameter.
• Color: The cysts are usually skin-colored or slightly yellowish.
• Contents: If a cyst is punctured or incised, it will release a characteristic oily, yellowish or whitish, odorless liquid. This is a key feature that distinguishes it from other types of cysts.

Location

The cysts appear most frequently in areas of the body that have a high concentration of sebaceous glands. The most common locations include:

• The chest and upper trunk
• The armpits (axillae)
• The neck
• The upper arms
• The scrotum and groin area

Symptoms

The cysts are almost always painless and asymptomatic. They do not typically cause itching. The primary symptom is the cosmetic appearance of having many bumps on the skin.

Occasionally, a steatocystoma can become inflamed and painful if it ruptures under the skin, triggering an inflammatory reaction. This can cause a red, tender lesion that may be mistaken for an infected acne cyst or a small boil.

Patients often come in thinking it’s severe acne, especially when the cysts become inflamed. But the telltale sign is that they’re deep, uniform, and don’t respond to acne treatments.

The diagnosis of steatocystoma multiplex is mostly clinical, based on appearance and family history.

• A dermatologist can typically identify the condition based on a physical examination, noting the characteristic appearance, feel, and distribution of the multiple cysts.
• The patient’s history is also key. The onset of the cysts around puberty and a family history of similar skin bumps are highly suggestive of the diagnosis.

In some cases, the doctor may perform a simple in-office procedure to confirm the diagnosis:

• Needle Aspiration: A small needle can be inserted into one of the cysts to draw out some of its contents. The presence of the signature oily, yellowish fluid is a strong confirmation.
• Skin Biopsy: If the diagnosis is uncertain, a single cyst may be surgically removed (excised) and sent to a laboratory. A pathologist will examine the cyst under a microscope and can identify the specific features of a steatocystoma, confirming the diagnosis.

I rarely need a biopsy unless there’s uncertainty or unusual presentation. Once you’ve seen steatocystoma multiplex a few times, the diagnosis becomes more recognizable.

There is no cure for steatocystoma multiplex. Treatment is usually for cosmetic reasons or symptom relief. It is also important for patients to know that there are no creams, lotions, or oral medications that can make existing cysts go away or prevent new ones from forming. The only way to address the cysts is procedural removal.

There are several different removal techniques, each with its own pros and cons. A discussion with a dermatologist can help determine the best approach.

• No Treatment: For many individuals, the most appropriate management is simply reassurance from their doctor about the benign nature of the condition.
• Incision and Drainage: A doctor can make a small cut in a cyst and express its oily contents. However, because the cyst wall is left behind, the cyst will almost always refill over time.
• Surgical Excision: To permanently remove a cyst, the entire cyst sac must be surgically cut out and the skin sutured closed. This is highly effective for individual cysts but is impractical for treating hundreds of lesions, as each excision leaves a small scar.
• Minimally Invasive and Advanced Techniques:
  • Mini-Incision with Expression: A tiny puncture is made, the contents are squeezed out, and then the collapsed cyst wall is pulled out with forceps.
  • Laser Therapy: CO2 lasers can be used to vaporize the cysts.
  • Cryotherapy: Using liquid nitrogen to freeze and destroy the cysts.

It is strongly advised that individuals do not try to squeeze or pop the cysts themselves. This can cause the cyst wall to rupture under the skin, leading to significant inflammation, pain, and an increased risk of scarring.

Most of my patients opt to leave the cysts alone unless they’re cosmetically troubling or inflamed. I usually advise against excessive excisions unless necessary. Scarring can be more bothersome than the cysts themselves.

Steatocystoma multiplex is a benign genetic condition that leads to the development of numerous, small, oil-filled cysts, typically on the trunk and upper body. While the appearance of these many bumps can be a source of significant cosmetic concern, it is important to remember that the condition is harmless, non-contagious, and does not develop into cancer. For many, reassurance of its benign nature is all that is needed. For those who wish to pursue treatment for cosmetic reasons, a variety of effective removal techniques are available. A consultation with a board-certified dermatologist is the best first step to confirm the diagnosis and discuss a personalized management plan that aligns with your cosmetic goals.

National Organization for Rare Disorders (NORD). (2021). Steatocystoma Multiplex. Retrieved from https://rarediseases.org/rare-diseases/steatocystoma-multiplex/

National Institutes of Health, Genetic and Rare Diseases Information Center (GARD). (2021). Steatocystoma multiplex. Retrieved from https://rarediseases.info.nih.gov/diseases/7679/steatocystoma-multiplex

DermNet NZ. (n.d.). Steatocystoma multiplex. Retrieved from https://dermnetnz.org/topics/steatocystoma-multiplex