What are the treatment guidelines for pityriasis rubra pilaris?

Treatment Guidelines for Pityriasis Rubra Pilaris

PUVA (psoralen-ultraviolet A) therapy is the first-line treatment for adult generalized pityriasis rubra pilaris, with systemic retinoids (particularly isotretinoin) recommended as first-line systemic therapy when phototherapy is not available or appropriate. 1

First-Line Treatment Options

Phototherapy

• PUVA therapy: Recognized as first-line phototherapy specifically for pityriasis rubra pilaris 1
  • Can be administered as oral PUVA or bath PUVA
  • Requires specialized phototherapy units with UVA capabilities
  • May be combined with topical treatments for enhanced efficacy

Systemic Therapies (when phototherapy is unavailable/inappropriate)

1. Retinoids:
   • Isotretinoin: First-line systemic therapy with excellent response rate of 61.1% 2
   • Dosing: Typically started at lower doses and titrated based on response
   • Monitoring: Requires lipid panel, liver function tests, and pregnancy prevention in women of childbearing potential

Second-Line Treatment Options

1. Methotrexate:

   • Recommended when retinoids fail or are contraindicated 2
   • Excellent response rate of approximately 33.1% 2
   • Dosing: Weekly administration (oral or subcutaneous)
   • Monitoring: CBC, liver and renal function tests

2. Combination therapy:

   • Retinoid + Methotrexate: Consider for cases resistant to monotherapy 3
   • Caution: Increased risk of hepatotoxicity requires careful monitoring

3. Other immunosuppressants:

   • Azathioprine: Alternative second-line option 3
   • Cyclosporine A: Particularly for rapidly progressing cases 3

Third-Line Treatment Options

1. Biologics:
   • Reserved for refractory cases that fail conventional therapies 3, 4
   • Options include:
     • TNF inhibitors: Infliximab (57.1% excellent response), etanercept (53.3%), adalimumab (46.4%) 2
     • IL-12/23 inhibitor: Ustekinumab (62.5% excellent response) 2
   • Can be used as monotherapy (81.1% success) or in combination with other systemics (87.5% success) 4

Treatment Algorithm

1. Initial assessment:

   • Confirm diagnosis through clinical presentation and histopathology
   • Evaluate disease extent and severity
   • Assess for contraindications to specific therapies

2. Treatment initiation:

   • For localized disease: Start with topical treatments (corticosteroids, calcipotriene)
   • For generalized disease:
     • If phototherapy available: Begin PUVA therapy
     • If phototherapy unavailable/contraindicated: Start isotretinoin

3. Evaluation of response (after 8-12 weeks):

   • If good response: Continue treatment until remission
   • If inadequate response: Move to second-line therapy

4. Second-line approach:

   • Switch to methotrexate OR
   • Consider combination of retinoid + methotrexate OR
   • Try azathioprine or cyclosporine A

5. For refractory disease:

   • Consider biologics (ustekinumab, infliximab, etanercept, or adalimumab)
   • May combine biologics with retinoids or methotrexate for enhanced efficacy

Important Clinical Considerations

• PRP is often misdiagnosed as psoriasis; careful differentiation is essential as treatment approaches may differ 1
• Classic PRP (Type I) typically has a better prognosis with appropriate treatment 3
• Continuous topical treatment should be maintained throughout systemic therapy 3
• Monitor for treatment-specific adverse effects:
  • Retinoids: Teratogenicity, hyperlipidemia, dry mucous membranes
  • Methotrexate: Hepatotoxicity, bone marrow suppression
  • Biologics: Infection risk, injection site reactions

Treatment Pitfalls to Avoid

1. Delayed diagnosis and treatment: Early diagnosis and prompt treatment with retinoids offer the best chance for clearing PRP 5

2. Inadequate treatment duration: PRP often requires longer treatment courses than psoriasis

3. Failure to recognize treatment side effects: As demonstrated in a case report, acitretin can rarely cause hypogammaglobulinemia 6

4. Misdiagnosis as psoriasis: PRP may be misdiagnosed as erythrodermic psoriasis, leading to inappropriate treatment choices 1

5. Relying solely on topical treatments for generalized disease: Systemic therapy is typically required for extensive disease

The treatment of PRP remains challenging due to its rarity and lack of randomized controlled trials. While these guidelines represent the current best evidence, treatment may need adjustment based on individual response and tolerability.