The cause of pityriasis rubra pilaris is unknown.
The two most common forms of the disorder are
Juvenile classic
Adult classic
The juvenile classic form of pityriasis rubra pilaris is inherited and begins in childhood. The adult classic form of pityriasis rubra pilaris does not seem to be inherited and begins in adulthood.
Other nonclassic forms exist in both age groups. Sunlight, human immunodeficiency virus (HIV) infection or another infection, minor trauma, or an autoimmune disorder may trigger a flare-up.
Symptoms of Pityriasis Rubra Pilaris
Symptoms of pityriasis rubra pilaris include pink, red, or orange-red scaly patches that can develop on any part of the body and are usually itchy. The skin can become thick and yellow.
Diagnosis of Pityriasis Rubra Pilaris
A doctor's evaluation
Skin biopsy
Doctors base the diagnosis of pityriasis rubra pilaris on how the scaly patches look and where they appear on the body.
Doctors sometimes take a sample of skin tissue and examine it under a microscope (biopsy) to rule out other disorders (such as seborrheic dermatitis Seborrheic Dermatitis Seborrheic dermatitis is chronic inflammation that causes yellow, greasy scales and dandruff to form on areas of the skin that have a high number of oil glands such as the scalp and face, along... read more 
in children and psoriasis Psoriasis Psoriasis is a chronic, recurring disease that causes one or more raised, red patches that have silvery scales and a distinct border between the patch and normal skin. A problem with the immune... read more 
).
Treatment of Pityriasis Rubra Pilaris
Medications applied to the skin (topical), taken by mouth (oral), or given by injection
Phototherapy
Treatment of pityriasis rubra pilaris is very difficult. Symptoms of the disorder may be lessened, but the disorder itself can almost never be cured. Classic forms of the disorder go away slowly over 3 years, whereas nonclassic forms last much longer.
To reduce scaling, doctors may give skin moisturizers Moisturizing agents (emollients) Topical drugs (drugs applied directly to the skin) are a mainstay of treating skin disorders. Systemic drugs are taken by mouth or given by injection and are distributed throughout the body... read more (emollients) or have people apply lactic acid under a dressing that keeps air away from the skin (occlusive dressing Occlusive dressings Topical drugs (drugs applied directly to the skin) are a mainstay of treating skin disorders. Systemic drugs are taken by mouth or given by injection and are distributed throughout the body... read more ), followed by corticosteroids Anti-inflammatory agents Topical drugs (drugs applied directly to the skin) are a mainstay of treating skin disorders. Systemic drugs are taken by mouth or given by injection and are distributed throughout the body... read more applied to the skin.
Acitretin or methotrexate taken by mouth is an option when treatments applied to the skin are not helping.
Etanercept, ustekinumab, and secukinumab are biologic agents that are given by injection. They may also be used if the skin does not improve with the topical or oral therapies.
Phototherapy Phototherapy Psoriasis is a chronic, recurring disease that causes one or more raised, red patches that have silvery scales and a distinct border between the patch and normal skin. A problem with the immune... read more (exposure to ultraviolet light), vitamin A, and medications that weaken the immune system, such as cyclosporine, mycophenolate mofetil, azathioprine, and corticosteroids taken by mouth, have also been used.
