PRP has an estimated prevalence ranging from 1 in 50,000 to 1 in 400,000 individuals worldwide. Both sexes are affected and there are two peak age groups:  childhood and middle adulthood (5th-6th decade). Most cases appear to be sporadic, although a familial form is associated with a gene mutation.

The exact cause of PRP is incompletely understood. Most cases occur sporadically with mild trauma, viral or bacterial infections, sunburn or autoimmune disease suspected as being possible triggers. A small percentage of cases are of a familial type inherited in autosomal dominant fashion (see RareShare guide on genetic inheritance) associated with mutations in the CARD14 gene which plays a role in inflammatory signaling pathways within the skin.

Clinical manifestations vary by subtype but commonly include

• Red-Orange Plaques: Broad patches of red to orange, sharply defined, scaling skin.

• Islands of Sparing: A hallmark sign of PRP where small patches of completely normal, unaffected skin appear within the larger areas of the red-orange rash.

• Follicular Hyperkeratosis: Small, rough, plugged hair follicles that feel like a "nutmeg grater," often appearing first on the elbows, knees, or the backs of the hands and fingers.

• Palmoplantar Keratoderma: Severe waxy, orange-red thickening of the skin on the palms of the hands and soles of the feet, which can crack and become painful.

• Pruritus (Itching): Can range from absent to severe.

• Nail Changes: Nails may become thickened, discolored, and show subungual hyperkeratosis (debris building up under the nail), though pitting (common in psoriasis) is rare.

In adult populations, PRP commonly begins on the head and neck and spreads downward, while in pediatric populations the disease may begin on the trunk or lower half of the body.

Diagnosis of PRP is primarily by clinical examination and may be supported by biopsy and histopathological evaluations to rule out similar conditions like psoriasis, skin allergies or cutaneous T-cell lymphoma. Characteristic orange-red plaques, follicular papules (small, raised lesions with rough texture), islands of sparing (areas of normal appearing skin surrounded by red-orange areas), and palmoplantar keratoma (excessive thickening of the skin in the palms and soles of the feet) may be observed. Microscopic examination of the skin may reveal areas of alternating anucleated and nucleated cells (orthokeratosis and parakeratosis) in a checkerboard pattern, thickened epidermis and plugged hair follicles.

There is no universally curative therapy for PRP. Treatment aims to reduce inflammation and improve skin function using a highly individualized approach that may include the following:

• Topical Therapies: Used for mild cases or as adjunctive therapy. This includes heavy emollients (moisturizers), keratolytics (like urea or salicylic acid to break down thick skin), topical corticosteroids, Vitamin D analogs, and topical retinoids.

• Systemic Oral Medications: Often the first-line treatment for moderate to severe cases. Oral retinoids (like acitretin or isotretinoin) are frequently used to slow skin cell turnover. Methotrexate (an immunosuppressant) is another common option.

• Biologics: In recent years, targeted biologic therapies originally developed for psoriasis (such as TNF-alpha inhibitors, IL-17 inhibitors like secukinumab, and IL-23 inhibitors) have shown significant promise in treating stubborn or severe PRP.

• Phototherapy: Narrowband UVB or PUVA light may be used, though it must be approached with caution as phototherapy occasionally aggravates PRP.

• Supportive Care: Management of itching and pain, prevention of skin infection, nutritional and hydration support, and mental health support as needed.

The prognosis heavily depends on which of the six clinical classifications (Griffiths classification) the patient falls into:

• Type I (Classic Adult): The most common form (>50% of cases). It has the best prognosis. Up to 80% of patients experience spontaneous remission within 1 to 3 years.

• Type II (Atypical Adult): Accounts for about 5% of cases. Tends to be more chronic and can last for decades.

• Type III (Classic Juvenile): Usually resolves within 1 to 2 years.

• Type IV (Circumscribed Juvenile): Features localized patches (often on knees/elbows). It is chronic and may persist into adulthood.

• Type V (Atypical Juvenile/Familial): Onset is usually at birth or early childhood. Driven by genetic mutations, it is typically chronic and lifelong.

• Type VI (HIV-associated): Occurs in individuals with HIV. It is often resistant to standard treatments, though highly active antiretroviral therapy (HAART) can improve the condition.

PRP can have a strong negative effect on quality of life, and those affected are at elevated risk for depression and suicide, underscoring the importance of both dermatological and mental health support. 

1. Zhou, T., Al Muqrin, A., & Abu-Hilal, M. 2024. “Updates on Pityriasis Rubra Pilaris: A Scoping Review.” Journal of cutaneous medicine and surgery, 28(2), 158–166. https://doi.org/10.1177/12034754231223159.

2. Greiling TM, Syed HA. 2024. “Pityriasis Rubra Pilaris.” In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; Available from: https://www.ncbi.nlm.nih.gov/books/NBK482436/.

3. National Organization for Rare Disorders (NORD):  Pityriasis Rubra Pilaris.

4. DermNet NZ:  Pityriasis Rubra Pilaris.