Pityriasis rubra pilaris (PRP) is a rare skin disorder that causes constant inflammation and shedding of the skin. PRP can affect parts of your body or your entire body. The disorder may begin in childhood or adulthood and affects males and females equally.
There are six types of PRP.
Classical Adult Onset
This is the most common type of PRP, and it begins in adulthood. The symptoms usually go away after a few years. In some rare cases, the symptoms come back later.
Atypical Adult Onset
This type also begins in adulthood, but the symptoms may last for more than 20 years.
Classical Juvenile Onset
This form begins in childhood. The symptoms usually go away within a year, but may return later.
Circumscribed Juvenile Onset
This type of PRP begins in children before they reach puberty. It most commonly affects the palms of the hands, soles of the feet, knees, and elbows. The symptoms may go away during teenage years.
Atypical Juvenile Onset
This form of PRP is sometimes inherited. It’s present at birth or may develop during early childhood. The symptoms often last indefinitely.
This form of PRP is associated with HIV infection and is very difficult to treat.
The exact cause of PRP is unknown. PRP most commonly occurs spontaneously for no identifiable reason. While some cases of PRP are inherited, most are not. Inherited PRP tends to be more severe.
Classical adult onset PRP may be associated with underlying skin cancer. However, the rate of occurrence of skin cancer with classical adult onset PRP is unknown. If you have classical onset PRP, have your doctor check you for skin cancer to be safe.
According to the National Organization for Rare Disorders, early research suggests that PRP may occur due to an abnormality in the way the body processes vitamin A. However, more research needs to be conducted to determine if this is true. It’s also thought that PRP is connected to an atypical immune system response, according to the Genetic and Rare Diseases Information Center (GARD).
PRP can be inherited. You may inherit PRP if one of your parents passes down the defective gene that causes the disorder. Your parent may be a carrier of the defective gene, but not actually have the disorder. If one of your parents is a carrier of the defective gene, there is a 50 percent chance that the gene will be passed to you. However, you may not develop clinical PRP even if you inherit the defective gene.
PRP causes pink, red, or orange-red scaly patches on your skin. The patches are usually itchy. You may only have the scaly patches on parts of your body. The scaly patches most often occur on the elbows, knees, hands, feet, and 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 your entire body.
PRP is often mistaken for other more common skin conditions, such as psoriasis, or less common conditions, such as lichen planus and pityriasis rosea. Psoriasis is characterized by itchy, scaly patches typically red in color. However, unlike PRP, psoriasis can be more easily and successfully treated. Sometimes, it’s not until the scaly patches fail to respond to treatment that PRP is considered.
If your doctor suspects PRP, they may perform a skin biopsy to make a diagnosis. A skin biopsy is a medical procedure in which a small sample of skin is removed so that the doctor (or a consulting pathologist) can examine it under a microscope.
For the most part, PRP can be itchy and lead to discomfort, which can decrease over time even if the rash looks like it’s getting worse. Typically, there are few complications, but according to PRP Support Group, the rash can lead to other conditions, such as ectropion. In this condition, the eyelid turns out, exposing the surface of the eye. The condition can also cause problems with the lining in the membrane of the mouth, leading to irritation and pain.
Over time, PRP can cause a condition called keratoderma in which the skin on the hands and soles of the feet becomes very thick. Fissures, or deep cracks in the skin can develop. Some people with PRP are sensitive to light and have trouble sweating or regulating body temperature when it’s hot.
There is no cure for PRP. Treatment consists of relieving the symptoms that accompany PRP. Your doctor may prescribe one or more of the following treatments to relieve symptoms:
- topical creams that contain urea or lactic acid
- oral vitamin A (effectively reduces or relieves symptoms in one-third of patients, according to GARD)
- oral retinoids like isotretinoin or acitretin (retinoids are medications that slow the growth and shedding of skin cells)
- biologics (medications that affect the immune system, such as Humira, Enbrel, Remicade)
- ultraviolet light therapy, which is usually prescribed in combination with Psoralen (a medication that makes you less sensitive to the sun) and a retinoid
Because the cause and onset of PRP are unknown, you cannot prevent this condition. Getting a diagnosis and finding a treatment that works for you as soon as you show signs and symptoms are key to a good outlook. This is especially important as it’s possible to 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 (the most common form of the disorder), your symptoms will most likely last a few years (or less) and then never return. Treatments may make symptoms less noticeable.