Pityriasis Rubra Pilaris: 6 Types, Symptoms & Treatment
Rare chronic skin disorder featuring orange-red scaly plaques, keratoderma, and islands of spared skin.
What is pityriasis rubra pilaris?
Pityriasis rubra pilaris is a rare chronic skin disorder characterised by reddish orange scaly plaques and keratoderma on the palms and soles, with islands of spared skin within areas of diffuse erythema.
Pityriasis rubra pilaris (PRP) represents 1.4% of all referrals for patch testing in one study, and 0.3% of all consultations in another study. It affects 1:3500–5800 dermatology patients.
The course of the disease is variable; classic type I adult-onset PRP often remits spontaneously within 3 years, whereas atypical type II may persist lifelong.
Who gets pityriasis rubra pilaris?
Pityriasis rubra pilaris affects all ages and ethnic groups.
- Adult-onset PRP (type I) is the most common form, representing 50–64% of cases. It usually starts gradually in adults aged 30–50 years.
- Childhood-onset PRP (type III) comprises 9–10% of cases and has an abrupt onset.
- Circumscribed juvenile PRP (type IV) affects 25% of paediatric cases and usually starts before age 12 years.
- HIV-associated PRP (type V) affects adults, particularly males.
There is no gender predilection.
What causes pityriasis rubra pilaris?
The cause of pityriasis rubra pilaris is not fully understood.
- Acquired PRP (types I, III, V, VI): Autoimmune disease triggered by infections, trauma, medications, vaccinations, or malignancy.
- Inherited PRP (types II, IV): Autosomal dominant mutations in CARD14 gene leading to constitutive NF-κB activation.
Abnormal keratinocyte proliferation and differentiation contribute to hyperkeratosis and parakeratosis.
What are the clinical features of pityriasis rubra pilaris?
Pityriasis rubra pilaris has six clinical types based on onset, course, and morphology.
Type I classical adult
Most common (50%). Gradual onset over weeks. Cephalocaudal spread: forehead, cheeks, elbows, knees, then trunk and extremities. Features:
- Orange-red follicular papules coalesce into plaques with cayenne-pepper spots.
- Yellow-brown palmoplantar keratoderma (painful fissuring).
- Islands of spared skin (pathognomonic).
- Erythroderma (70%).
- Pruritus (50%).
- Onycholysis, yellow nail discolouration (subungual hyperkeratosis).
- Sparse hair, eyebrows, eyelashes.
Remits in 80% within 3 years.
Type II atypical adult
5% of cases. Persistent erythroderma with ichthyosiform scaling. Less follicular involvement, more debilitating keratoderma. Lifelong course.
Type III classical juvenile
5%. Abrupt onset pink follicular papules. Resolves within 1 year.
Type IV circumscribed juvenile
25% of juvenile cases. Hyperkeratotic plaques on knees, elbows, dorsal fingers. Resolves by adulthood.
Type V HIV-associated
Affects HIV patients. Nevoid follicular hyperkeratosis, severe palmoplantar keratoderma.
Type VI Follicular
Non-scaly follicular spinous papules, scarring alopecia, periorificial seborrhoeic dermatitis-like plaques.
Diagnosis of pityriasis rubra pilaris
Clinical diagnosis based on:
- Orange-red scaly plaques
- Palmoplantar keratoderma
- Islands of spared skin
- Follicular keratotic plugs
- Cobblestone elbow/knee papules
Dermoscopy: Red-orange background, white scaling, follicular plugs.
Histology (if atypical): Alternating ortho/parakeratosis, follicular plugging, acanthosis, upward epidermal elongation.
Differential diagnosis: Psoriasis, eczema, lichen planus, seborrhoeic dermatitis, cutaneous T-cell lymphoma, ichthyoses.
Biopsy of pityriasis rubra pilaris
Features:
| Feature | Description |
|---|---|
| Epidermis | Acanthosis, elongated rete ridges |
| Stratum corneum | Alternating ortho/parakeratosis (shoulder parakeratosis) |
| Follicles | Keratotic plugging |
| Dermis | Perivascular lymphocytic infiltrate |
Psoriasiform but lacks Munro microabscesses, regular parakeratosis.
Treatment of pityriasis rubra pilaris
No cure; aim to reduce inflammation, hyperproliferation, symptoms. Multimodal approach.
Topical therapy
- Emollients: Essential for xerosis.
- Corticosteroids: Potent for inflammation (limited efficacy).
- Vitamin D analogues (calcipotriol): Reduce scaling.
- Tazarotene: Retinoid gel for plaques.
Phototherapy
- Narrowband UVB, PUVA, Re-PUVA (with retinoids).
- Extracorporeal photopheresis (ECP).
Systemic therapy
| Agent | Efficacy | Notes |
|---|---|---|
| Acitretin (retinoid) | 36–60% good response | First-line; 0.5–1 mg/kg/day. Teratogenic. |
| Methotrexate | 33–50% | Immunosuppressant; 10–25 mg/week. |
| Biologics | IL-17/23 inhibitors (ixekizumab 61%, secukinumab) | TNF-α (adalimumab), ustekinumab. |
| Cyclosporine, azathioprine | Variable | Second-line. |
Oral steroids ineffective. No FDA-approved treatments.
What is the outcome for pityriasis rubra pilaris?
- Type I: 80% remit in 3 years.
- Type II: Lifelong.
- Juvenile types: Resolve by adulthood.
- Postinflammatory hyperpigmentation, scarring possible.
Frequently asked questions
Is pityriasis rubra pilaris the same as psoriasis?
No. PRP has islands of spared skin, follicular papules, alternating parakeratosis on biopsy; psoriasis has regular parakeratosis, Munro microabscesses.
Is pityriasis rubra pilaris itchy?
Pruritus in 50% (type I); early rash itchy, later less so.
Is pityriasis rubra pilaris hereditary?
Types II/IV inherited (CARD14); most sporadic.
Does pityriasis rubra pilaris go away?
Type I: 80% remit 3 years; type II persists.
Can pityriasis rubra pilaris be cured?
No cure; managed with therapy. Spontaneous remission common in classic forms.
References
- Pityriasis Rubra Pilaris — NORD (National Organization for Rare Disorders). 2023. https://rarediseases.org/rare-diseases/pityriasis-rubra-pilaris/
- Pityriasis Rubra Pilaris — StatPearls, NCBI Bookshelf. 2023-10-15. https://www.ncbi.nlm.nih.gov/books/NBK482436/
- Pityriasis rubra pilaris — DermNet NZ. 2024. https://dermnetnz.org/topics/pityriasis-rubra-pilaris
- Pityriasis Rubra Pilaris — JAMA Dermatology. 2020-01-08. https://jamanetwork.com/journals/jamadermatology/fullarticle/2723286
- Pityriasis Rubra Pilaris – Skin Disorders — Merck Manuals. 2024. https://www.merckmanuals.com/home/skin-disorders/psoriasis-and-scaling-disorders/pityriasis-rubra-pilaris
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