Porokeratosis refers to a group of skin conditions that typically appear as small patches with a raised edge.

There are six main subtypes of porokeratosis, which vary in color, size, and where they appear on the body. In most cases, porokeratosis is not a cause for concern. However, there is a risk that cells in the affected areas may become cancerous.

Read on to find out more about porokeratosis, including its diagnosis, treatment, and causes.

The term porokeratosis encompasses a range of skin conditions in which the area develops pink, red, or brown bumps with a raised edge. In some cases, porokeratosis may affect one area or appear in multiple places.

Porokeratosis is not contagious, and although it may develop in multiple places, it is unlikely to spread from one part of the body to another through contact.

Porokeratosis is a precancerous condition, with all its variants having the potential for the cells to transform into cancer.

There are six main subtypes of porokeratosis:

Disseminated superficial actinic porokeratosis (DSAP)

The most common subtype of porokeratosis, DSAP usually appears in people in their 20s or 30s. It is more common in females than in males.

In terms of appearance, DSAP is more extensive than other subtypes and appears as reddish and brown spots. These tend to appear symmetrically across a person’s back, arms, legs, and shoulders.

A variety of factors may cause DSAP to develop. The main cause seems to be exposure to ultraviolet (UV) light. However, people may also have an inherent genetic risk of developing this type of porokeratosis.

There is a 3% risk that a person with DSAP will develop skin cancer.

Mibelli porokeratosis

Mibelli porokeratosis is the second most common subtype of porokeratosis, and it typically develops in children or young adults. Older research suggests that it is twice as common in males than in females.

Mibelli porokeratosis appears as discolored raised skin bumps with a thin border. These often develop on the torso, arms, or legs. Although they are usually only a few centimeters in size, in some cases, they may enlarge over time.

There is an 8% chance that Mibelli porokeratosis will develop into cancer.

Disseminated superficial porokeratosis (DSP)

DSP is one of the rarer subtypes of porokeratosis and tends to manifest in childhood.

DSP is similar to DSAP, and they share the same appearance. However, whereas DSAP appears only in sun-exposed areas, DSP can also affect areas of the body that do not get exposure to the sun. Therefore, DSP can appear anywhere on the body.

Developing skin cancer following the manifestation of DSP is rare.

Linear porokeratosis

Linear porokeratosis is a rare form of porokeratosis that usually occurs in early childhood.

Linear porokeratosis is similar in appearance to DSP and DSAP, but it has the distinguishing feature of appearing along Blaschko lines. Blaschko lines are lines on the skin that show the pathways of fetal cell development.

There is a 19% risk that a person with linear porokeratosis will develop skin cancer.

Porokeratosis plantaris palmaris et disseminata (PPPD)

PPPD appears on the palms of the hand and soles of the feet as scaly circular patches. Sometimes, these may spread to the extremities and torso.

As PPPD is an extremely rare subtype of porokeratosis, there is a lack of research exploring its causes and potential triggers. However, older research suggests that people may inherit PPPD. Although it usually manifests during adolescence or a person’s early 20s, there have been cases of older individuals developing PPPD.

There is a 10% risk that a person with PPPD will develop skin cancer.

Punctate porokeratosis

Punctate porokeratosis is a skin condition that appears in adulthood in the form of many tiny, ridge-like bumps on the palms of the hands and soles of the feet.

These bumps may slowly spread over the skin and might cause itching or discomfort while walking.

Punctate porokeratosis is a very rare subtype of porokeratosis. For this reason, there is a lack of scientific research exploring its causes and triggers.

The diagnosis of porokeratosis typically involves a physical examination. A dermatologist will inspect the affected areas and possibly perform dermoscopy.

In some cases, a biopsy may also be necessary to rule out other conditions or check for cancerous cells.

Currently, there is no cure for porokeratosis. However, a person may undertake treatment to improve the appearance of the affected areas. A 2017 review of treatment for porokeratosis lists the following options:

  • Imiquimod cream: Imiquimod belongs to a group of drugs called immune response modifiers. They work by activating the immune system to fight abnormal skin growths.
  • Topical or systemic retinoids: Retinoids are medicines that derive from Vitamin A. A person with porokeratosis may require topical retinoids in the form of creams, lotions, or gels. Alternatively, a doctor may recommend oral retinoids.
  • Topical vitamin D: Applying vitamin D to the affected areas may provide some therapeutic benefits.
  • Procedural interventions: In some cases, procedural interventions, such as cryotherapy and laser therapy, may be necessary. However, doctors will only consider these options in extreme circumstances.

The exact causes of certain subtypes of porokeratosis are unknown. However, theories as to what causes porokeratosis include:

  • Genetic: One theory is that a person may inherit a defective gene that triggers the condition
  • Sunlight exposure: Older research suggests that sunlight or UV exposure may cause some forms of porokeratosis, including DSAP.
  • Immunosuppression: Conditions or treatments that result in a person having a weakened immune system may also trigger the development of some subtypes of porokeratosis.

A person with porokeratosis should consider limiting their sun exposure and regularly moisturizing the affected areas. They should also use sun cream with a high SPF.

Anecdotal evidence suggests that aloe vera may alleviate the itching that some people with certain subtypes of porokeratosis may experience.

However, even if this does reduce discomfort, a person should still consider seeing a dermatologist who can prescribe appropriate treatment.

A person experiencing porokeratosis should consider regularly visiting their doctor or dermatologist. These professionals can monitor the area and check for any signs of skin cancer developing.

In between regular checkups, a person should consider additional consultations with their doctor if they notice any sudden changes in the affected areas or the symptoms start to appear in additional parts of the body.

A person should also consider consulting their doctor if they experience any pain, itching, discoloration, or bleeding around the affected sites.

Porokeratosis is the general term for a group of skin conditions causing small, discolored bumps with a raised border to appear on the skin.

There is currently no cure for porokeratosis, but several treatments are available that help reduce the appearance of the bumps or lesions.

A person with porokeratosis should consider seeing a doctor or dermatologist. There is a risk that cancerous cells may develop, and these healthcare professionals can regularly monitor the affected areas to check for this outcome.