Steatocystoma Multiplex: A Complete Guide to Causes, KRT17 Genetics, Inflammation and Curative Surgery

Many patients arrive with the same puzzle: "I have dozens of little bumps on my chest and arms. Nothing comes out when I squeeze them, I've been treated several times for sebaceous cysts or acne, but they just won't go away." When dozens — sometimes hundreds — of similarly sized small cysts appear under the skin at once, this is often not ordinary acne or a simple cyst, but a specific benign condition: steatocystoma multiplex.

Key point: Steatocystoma multiplex is a benign cyst arising from the sebaceous duct. Each cyst contains oily sebum rather than keratin, which makes its origin different from an ordinary epidermoid cyst. It does not disappear on its own and cannot be cured by squeezing or medication; the only way to cure an individual lesion is to remove its entire cyst wall.

This guide walks you through steatocystoma multiplex: what it is, why it appears, its link to KRT17 (keratin 17) and inheritance, why some lesions become recurrently inflamed, and how to approach treatment when there are many lesions.

What is steatocystoma multiplex?

A steatocystoma is a cyst sitting in the dermis whose wall is made of a distinctive epithelium and carries sebaceous glands (the oil-producing glands) within the wall itself; its contents are oily sebum. When only a single cyst appears without a family pattern, it is called steatocystoma simplex; when many appear across the body at once, it is steatocystoma multiplex.

Its typical appearance is:

• Numerous: from a dozen to over a hundred, often in clusters
• Small and uniform: most are 0.3–1 cm across, felt as soft to moderately firm, movable nodules under the skin
• Color: skin-toned, pale yellow, or with a faint blue-grey tint
• Usually no central punctum (the small surface opening): this is one feature that distinguishes them from ordinary cysts

The usual age of onset is adolescence to early adulthood. Sebaceous glands become active under androgen stimulation during puberty, which is why steatocystomas tend to surface during this stage.

Steatocystoma is not an ordinary cyst: clearing up the most common confusion

Clinically, steatocystoma multiplex is most often mistaken for "having lots of sebaceous cysts," but the two differ in origin and contents:

For a detailed comparison and why telling them apart changes how they are treated, see: Steatocystoma vs Epidermoid Cyst: the key differences in origin, contents and treatment→. If you are still unsure which kind you have, you can also compare symptoms in the Complete Guide to Epidermoid Cysts→.

Why does it appear? The KRT17 gene and inheritance

The most studied cause of steatocystoma multiplex is variation in the KRT17 gene.

KRT17 produces keratin 17 — a protein that keeps the cell skeleton of skin, hair follicles and sebaceous glands stable. When this gene is altered, the keratin network cannot form a stable structure, and the development and function of the sebaceous duct are disrupted, giving rise to sebum-filled cysts.

Is it inherited?

It can be, but not in every case.

• Familial form: autosomal dominant inheritance — if one parent carries the variant, each child has roughly a 50% chance of inheriting the same tendency. In the familial form, the KRT17 variant lies in the same region as the gene for an inherited nail disorder, pachyonychia congenita type 2, so a small number of familial patients may also have thickened nails.
• Sporadic form: many patients have no clear family history, with a spontaneous variant or constitutional tendency that presents simply as steatocystoma multiplex without other systemic problems.

Key point: "Multiple" does not mean "definitely inherited." Those with a family history and a dominant pattern do carry roughly a 50% risk for their children; but the sporadic form is also common. Rather than guessing from the number of lesions, it is better to have the lesions assessed and discuss family screening if needed.

Where it appears, and three clinical types

Steatocystoma multiplex appears most often in areas dense with sebaceous glands:

• The chest (especially around the sternum), upper arms and axillae
• The neck, upper back and abdomen
• The scrotum and thighs in men

Clinically it is grouped into a few types:

Why is the inflamed (suppurativa) type so troublesome?

Some steatocystomas repeatedly become inflamed, rupture and suppurate, forming what is called the suppurativa type of steatocystoma multiplex. The difficulty with this type is:

1. Recurrent redness and pain: when a cyst ruptures, leaked sebum irritates surrounding tissue and triggers inflammation
2. A tendency to scar: repeated inflammation and improper squeezing cause fibrosis, pigmentation, and even depressed or raised scars
3. Cosmetic and emotional burden: it favours the chest and upper arms — areas that are hard to cover — with a clear effect on appearance and confidence

⚠️ Caution: Do not squeeze or pick at an inflamed steatocystoma yourself. Squeezing only expels part of the contents; the wall remains and quickly refills, and it may worsen inflammation, spread infection and leave a more obvious scar. During a flare, see a doctor first to assess whether the inflammation should be settled before planning treatment.

The curative approach: surgery that removes the entire cyst wall

The various treatments for steatocystoma multiplex actually have different goals:

The key is this: as long as the cyst wall remains, sebum keeps accumulating and that lesion can return. So to make an individual lesion stop recurring for good, the curative approach is to remove the entire cyst wall. Medication and laser can help control inflammation or improve appearance, but they cannot replace the role of complete surgical removal of the wall.

Because steatocystoma multiplex often presents as dozens of lesions at once, treatment requires not just "cutting them out" but an overall plan that balances number, wounds and scarring. Before surgery, using ultrasound guidance to see the depth and extent of each cyst→ helps plan the incisions and priorities.

How Liusmed approaches it: many lesions, but every wound kept as small as possible

Steatocystomas of the multiplex type are usually under 1 cm, and Liusmed keeps each incision within 0.5 cm (most can be removed whole through just 0.3 cm). The more lesions there are, the more this very-small-incision strategy matters:

• So patients never trade a body of cysts for a body of scars: with dozens across the chest and both arms, traditional large incisions add up to a sheet of scarring; keeping each incision at 0.3–0.5 cm lets scars tuck into the skin's natural lines (scar-minimizing removal)
• Removing the whole wall to reduce recurrence of that lesion: even with a tiny incision, the goal is still to remove the entire cyst wall, not just express the contents
• Staged planning by priority: it does not all have to be cleared at once — frequently inflamed, cosmetically prominent or sensitively located lesions can be treated first, with the rest followed up regularly

For details on minimal-incision removal of many small cysts and post-op scar care, see: Will steatocystoma multiplex leave lots of scars? 0.5 cm scar-minimizing removal and aftercare→.

Key point: The point of treating steatocystoma multiplex is not just to clear the cysts, but to clear them without leaving a conspicuous sheet of scarring. That is the intent behind keeping each incision at 0.3–0.5 cm — Liusmed is one of the few clinics in Taiwan focused on scar-minimizing removal of steatocystoma multiplex.

Frequently asked questions

Q: Will steatocystoma multiplex go away on its own?

No. The cyst wall is a stable structure and sebum keeps accumulating within it, so a steatocystoma does not resolve by itself. It may swell temporarily during inflammation and shrink afterwards, but the lesion itself remains.

Q: Can I squeeze them or lance them?

Not advisable. Squeezing only expels part of the sebum; the wall remains and quickly refills, and it can trigger inflammation, infection and a more obvious scar. To eliminate an individual lesion, the whole wall still has to be removed.

Q: Can oral isotretinoin cure it?

Oral isotretinoin reduces sebum production and helps control the recurrently inflamed suppurativa type, but the cysts remain after stopping the drug; it cannot replace the curative role of complete surgical removal of the wall. Whether to use it, the dose and monitoring must be assessed by a doctor.

Q: Will I pass it on to my children?

If you have the KRT17-related familial form with a dominant pattern, each child has roughly a 50% chance of inheriting the same tendency; the sporadic form has no clear inherited link. It is better to be assessed and discuss family screening if needed, rather than judging by the number of lesions.

Q: Do dozens of lesions all have to be treated at once?

Not necessarily. They can be staged by priority after ultrasound assessment: treat the recurrently inflamed, cosmetically prominent or sensitively located lesions first, and follow up the rest. The key is to keep every incision as small as possible so scars tuck into the skin's natural lines.

Ready for a closer assessment? You are welcome to book a consultation with Dr. Ta-Ju Liu for a full ultrasound evaluation and a steatocystoma multiplex treatment plan→.

All information in this article is for educational reference only and does not constitute medical advice or diagnosis. If you have concerns about a lump under the skin or recurrently inflamed cysts, please consult a qualified physician for assessment.