Pityriasis rubra pilaris (PRP) is a rare skin disease. It causes constant inflammation and shedding of the skin. PRP can affect parts of your body or your entire body. The disorder may start in childhood or adulthood. PRP affects males and females equally.

There are six types of PRP.

Classical adult onset PRP is the most common type. It occurs in adulthood. The symptoms usually go away after a few years. In some rare cases, the symptoms come back later.

Atypical adult onset PRP also begins in adulthood. However, the symptoms may last more than 20 years.

Classical juvenile onset PRP starts in childhood. The symptoms normally go away within one year, but they may come back later.

Circumscribed juvenile onset PRP begins before puberty. It most commonly affects the palms of children’s hands, the soles of their feet, and their knees and elbows. The symptoms may go away during the teenage years.

Atypical juvenile onset PRP is sometimes inherited. That means it’s passed on through the family. It can be present at birth or develop during early childhood. The symptoms often last for life.

HIV-associated PRP is linked with HIV. It’s very difficult to treat.

The exact cause of PRP is unknown. PRP most often occurs for no clear reason. While some cases of PRP are inherited, most aren’t. Inherited PRP tends to be more severe.

Classical adult onset PRP may be linked with underlying skin cancer. However, how often skin cancer happens with this type of PRP is unknown. If you have classical onset PRP, make sure you see your doctor to check for skin cancer.

According to the National Organization for Rare Disorders, early research suggests that PRP may be due to a problem in the way the body processes vitamin A. However, more research is needed to figure out if this is true.

PRP may also be connected to an immune system response, according to the Genetic and Rare Diseases Information Center.

PRP can be inherited. You may inherit PRP if one of your parents passes down the gene that causes the disorder. Your parent may be a carrier of the gene, which means they have the gene but don’t have the disorder. If one of your parents is a carrier of the gene, there’s a 50 percent chance that the gene was passed to you. However, you may not develop PRP even if you inherited the gene.

PRP causes pink, red, or orange-red scaly patches on your skin. The patches are usually itchy. You may have the scaly patches on only some parts of your body. They most often occur on the:

  • elbows
  • knees
  • hands
  • feet
  • ankles

The skin on the palms of your hands and the soles of your feet may also become red and thickened. The scaly patches may eventually spread over the entire body.

PRP is often mistaken for other, more common skin conditions, such as psoriasis. It can also be mistaken for less common ones, such as lichen planus and pityriasis rosea. Psoriasis is marked by itchy, scaly patches of skin that are often red. However, unlike PRP, psoriasis can be more easily and successfully treated. PRP may not be diagnosed until the scaly patches fail to respond to psoriasis treatment.

If your doctor suspects PRP, they may do a skin biopsy to help them make a diagnosis. For this procedure, your doctor removes a small sample of your skin. They then look at it under a microscope to analyze it.

For the most part, PRP can be itchy and uncomfortable. These symptoms can decrease over time, even if the rash looks like it’s getting worse. The condition usually doesn’t cause many complications.

However, PRP Support Group notes that the rash can sometimes lead to other issues, such as ectropion. In this condition, the eyelid turns out, exposing the surface of the eye. PRP can also lead to problems with the lining of the mouth. This can result in irritation and pain.

Over time, PRP can lead to keratoderma. This issue causes the skin on your hands and soles of your feet to become very thick. Deep cracks in the skin, called fissures, can develop.

Some people with PRP are also sensitive to light. They may have trouble sweating or controlling their body temperature when it’s hot.

There’s no current cure for PRP, but treatment can relieve symptoms. Your doctor may prescribe one or more of the following treatments:

  • Topical creams containing urea or lactic acid. These go directly on your skin.
  • Oral retinoids. Examples include isotretinoin or acitretin. These are derivatives of vitamin A that slow the growth and shedding of skin cells.
  • Oral vitamin A. This may be helpful in some people, but only in very high doses. Retinoids are more effective and more commonly used than vitamin A.
  • Methotrexate. This is an oral drug that may be used if retinoids don’t work.
  • Immunosuppressants. These are oral medications that suppress the immune system. They include cyclosporine and azathioprine.
  • Biologics. These are injectable or intravenous (IV) medications that affect your immune system. They include the drugs adalimumab, etanercept, and infliximab.
  • Ultraviolet light therapy. This is normally given in combination with psoralen (a drug that makes you less sensitive to the sun) and a retinoid.

It’s not possible to prevent PRP since the cause and onset are unknown. If you suspect you have PRP, see your doctor. Starting a treatment that works for you as soon as you get a diagnosis is key to relieving your symptoms.

Finding an effective treatment is also important because you may develop more than one type of PRP over the course of the disease.

Depending on the type of PRP you have, your symptoms may or may not go away. If you have classical adult onset PRP, your symptoms will likely last a few years or less and then never return.

The symptoms of other PRP types may be more long-lasting. However, treatments may make symptoms less noticeable.

PRP is a rare skin disease marked by constant inflammation and shedding of your skin. It may affect your entire body or just parts of it. It can start at any time during your life. Although there’s no current cure, treatments may help ease your symptoms.

Treatments for PRP include topical, oral, and injectable medications. They also include ultraviolet light therapy. Work with your doctor to find the treatment that works best to relieve your symptoms of PRP.