Porokeratosis: What’s the Risk of Cancer?

Anna Giorgi
·8 min read
<p>Matt Lincoln / Getty Images</p>

Matt Lincoln / Getty Images

Medically reviewed by William Truswell, MD

"Porokeratosis" refers to a group of rare skin diseases that result in an overabundance of a protein called keratin. These ailments cause small, scaly papules (raised bumps) that have a thin, raised border that is white, yellow, or brown. The bumps can occur alone or expand to create patches.

This disease can be caused by genetic or acquired factors. Bumps often appear on your arms and legs, though they can occur on any part of your body. They can happen in one section or spread to more than one area.

Treatment is often not needed, though itchy bumps can be relieved. It is also possible to remove the bumps. Though rare, porokeratosis can become malignant (cancerous).

This article describes porokeratosis causes, symptoms, and diagnosis. It also covers the need for treatment and what can be done.

<p>Matt Lincoln / Getty Images</p>

Matt Lincoln / Getty Images

Link Between Porokeratosis and Cancer

While the general prognosis for most people with porokeratosis is good, research indicates that the disease can be precancerous. Studies show that the skin changes can create a high risk of skin cancer for those affected.

Research indicates that 6.9% to 11.6% of porokeratosis cases develop into skin cancer. The most common type of skin cancer to occur from porokeratosis is squamous cell carcinoma, though it is also linked with basal cell carcinoma and melanoma.

The risk of skin cancer for porokeratosis is low overall. Of the six subtypes of porokeratosis, the highest risk of becoming skin cancer exists with the disseminated superficial actinic porokeratosis (DSAP) variant. Skin cancer has also resulted from porokeratosis of Mibelli and linear porokeratosis.

Learn More: What Does Skin Cancer Look Like?

Causes: Why Does Porokeratosis Form?

The specific cause of porokeratosis is unknown. It is thought to occur from an abnormal reproduction of keratinocytes—cells that make up the majority of your epidermis (the outermost layer of your skin). It is not a contagious condition.

The following characteristics are regarded as risk factors for porokeratosis:

How Different Types of Porokeratosis Look

There are six types of porokeratosis. Symptoms for each variant include the following:

Classic porokeratosis of Mibelli characteristics include:

  • Generally affects children or young adults (more common in males than females)

  • Begins as one or a few small, brownish bumps

  • Develops into raised, bumpy patches that increase in size over time

  • Patches show a prominent border with a thin ridge with white, yellow, or brown edges that are easily identified

  • Lesions located on your trunk or a limb, though they can develop anywhere

  • Pruritus (abnormal itching)

  • Skin atrophy (erosion of epidermis, resulting in lax, wrinkled, and shiny skin with visible underlying veins)

  • Hyperkeratosis (a skin condition in which the outer layer of skin becomes thick and hard due to too much keratin)

Disseminated superficial porokeratosis (DSP) characteristics include:

  • Generally affects children ages 5 to 10 years

  • Ring-shaped brownish lesions on both sun- and non-sun-exposed areas

  • Numerous skin lesions, mainly on the trunk, genitals, and ends of the arms and legs

  • Lesions can appear bilateral and symmetrical

  • Pruritus

  • Hyperkeratosis

  • Skin atrophy

Disseminated superficial actinic porokeratosis (DSAP) characteristics include:

  • Generally affects adults in their 30s and 40s (more common in females than males)

  • Multiple small, round, pink to reddish brown lesions that can total in the hundreds

  • Lesions present on any part of the body, though most often on the arms, legs, shoulders, or back

  • Severe pruritus and/or stinging

  • Skin patches with a scaly appearance

  • Symptoms worsen during the summer or after phototherapy

Porokeratosis palmaris et plantaris disseminata (PPPD) characteristics include:

  • Generally affects adolescents and young adults (more common in males than females)

  • Small, skin-colored lesions that are flat and may merge with surrounding skin

  • Lesions may have yellow pits in their center

  • Lesions are often bilateral and symmetrical

  • Numerous lesions measuring 1 to 2 millimeters (mm) on your palms and soles, possibly spreading to affect larger areas

  • May also include DSAP-like lesions on your trunk and limbs or mucous membranes

  • Skin atrophy

  • Possible painful lesions

Linear porokeratosis (LP) characteristics include:

  • Generally affects children and occasionally adults (more common in females than males)

  • Multiple small reddish-pink skin lesions, usually limited to small areas of your body

  • Formation of lesions in a linear distribution on your extremities

  • Lesions that start on your palms and soles but spread to other parts of your body

  • Skin atrophy

  • Pruritus

Punctate porokeratosis (PP) characteristics include:

  • Generally affects adolescents and young adults

  • Multiple seed-like lesions that measure 1 to 2 mm on your palms and soles

  • Depressed or raised lesions

  • Linear or diffused pattern to lesion placement

  • Pruritus or tenderness

  • Possibly present with other forms of porokeratosis





Porokeratosis vs. Ringworm

The lesions caused by porokeratosis are round with a border that can be confused with ringworm. However, these conditions differ in the following ways:

Porokeratosis;

  • Caused by genetics or acquired by factors related to sun exposure

  • Not contagious

  • Center bump that is pink to brown

  • Symptom relief with dermatologist-prescribed therapies or procedures

Ringworm:

  • Caused by a fungus

  • Highly contagious through skin-to-skin contact

  • The center bump is the same color or slightly lighter than your skin color

  • Treatable at home with an over-the-counter antifungal cream




Biopsy to Diagnose Porokeratosis

The hallmark of all types of porokeratosis is the coronoid lamella, the thin raised edge that surrounds a lesion. A diagnosis can be made if the coronoid lamella is present.

A dermatologist (a physician specializing in skin conditions) can usually make a diagnosis based on the presence of the coronoid lamella, a visual examination, and the use of dermoscopy (a skin examination using a handheld magnifying device called a dermatoscope used to diagnose skin cancer).

However, a skin biopsy is sometimes used to achieve a definitive diagnosis if there is any doubt. A biopsy can also be helpful if a spot has characteristics such as crusting, redness, or scaling that may indicate that it poses a risk of skin cancer.

When a biopsy is performed, a sample is taken from the border of the lesion. When porokeratosis exists, the sample shows cells from the coronoid lamella.

How to Protect Skin With Porokeratosis

While multiple treatments are used for porokeratosis, there are no treatment standards. Treatment is individualized based on a person's functional and aesthetic concerns.

If you have a diagnosis of porokeratosis, it is important to follow up with a dermatologist to monitor your lesions in case they become cancerous. You should also avoid additional damage to the affected area so you don't aggravate the condition.

The following strategies can help protect skin that is diagnosed with porokeratosis:

  • Avoid exposure to the sun between the hours of 10 a.m. and 4 p.m., when the sun is strongest.

  • Apply sunscreen with a sun protection factor (SPF) of 30 or higher daily, regardless of the weather.

  • Reapply sunscreen every two hours and after swimming or sweating heavily.

  • Remain in the shade of an umbrella, tree, or other type of shelter when you are outside during daylight hours.

  • Wear a hat, long-sleeved shirts, and long pants out in the sun.

  • Choose clothing with tightly woven materials, which provide greater protection from the sun.

  • Avoid reflective surfaces like sand, water, and concrete that can reflect more than half of the sun's rays onto your skin.

  • Do not use tanning parlors since the ultraviolet (UV) light emitted by tanning booths can increase your risk of skin cancer.

There is no evidence that home remedies can cure porokeratosis. You may achieve some symptom relief with the use of emollients, which can help soften the appearance and texture of rough, hard lesions. Consult with your dermatologist for additional treatment options.

Treatment for Porokeratosis at the Dermatologist

Mild cases of porokeratosis do not require treatment. Treatment for porokeratosis is elective. It is usually done to treat discomfort and/or cosmetic concerns. While treatments are effective, achieving full remission (absence of disease symptoms) can be challenging.

Responses to different treatments vary by individual and are usually temporary. Only about 16% of people treated achieve a complete response. Relapses are common.

The best way to treat your condition may depend on the type of porokeratosis you have. The following treatments for porokeratosis are some of the most commonly used options available from your dermatologist:

Topicals:

Oral medication:

Procedures:

Summary

Porokeratosis includes a group of diseases that cause small, scaly lesions on your skin. These round bumps can grow alone or in patches. They are defined by a raised border and can become itchy.

This group of skin conditions can be present at birth or acquired. Risk factors include exposure to UV light, a weakened immune system, infections, certain drugs, and trauma to your skin.

There is no cure for porokeratosis. Treatment for mild cases is not needed. Therapy is geared toward relieving symptoms such as itching. It can also help improve appearance by reducing the number of lesions, though recurrence is common.