What is the optimal biologic therapy for a young adult woman with existing plaque psoriasis and newly diagnosed small‑bowel Crohn’s disease?

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Last updated: February 13, 2026 • View editorial policy

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Optimal Biologic Therapy for Concurrent Psoriasis and Small Bowel Crohn's Disease

Ustekinumab is the definitive first-line biologic for a young woman with both psoriasis and newly diagnosed small bowel Crohn's disease, as it is the only agent with FDA approval and proven efficacy for both conditions. 1, 2

Primary Recommendation

Start ustekinumab using the Crohn's disease induction protocol: a single intravenous infusion based on weight (260 mg if ≤55 kg, 390 mg if 55-85 kg, or 520 mg if >85 kg), followed by 90 mg subcutaneous maintenance every 8 weeks beginning 8 weeks after the IV dose. 1 This dosing strategy addresses the more urgent Crohn's disease while simultaneously treating the psoriasis.

Why Ustekinumab is Superior in This Clinical Context

  • Dual FDA approval: Ustekinumab is approved for moderate-to-severe plaque psoriasis, psoriatic arthritis, Crohn's disease, and ulcerative colitis, making it uniquely suited for concurrent disease 1

  • Enhanced efficacy in concurrent disease: Retrospective data demonstrate that ustekinumab has greater efficacy in Crohn's disease patients with concurrent autoimmune skin disease compared to those without, with superior outcomes in fecal calprotectin (P=0.0337), endoscopy (P=0.016), and complete resolution of moderate/severe disease 3

  • Mechanism of action: By blocking the p40 subunit shared by IL-12 and IL-23, ustekinumab targets inflammatory pathways central to both psoriasis and Crohn's disease 4, 5

Alternative Agents and Why They Are Inferior

TNF-α Inhibitors (Infliximab, Adalimumab)

While infliximab and adalimumab have demonstrated efficacy in psoriasis, psoriatic arthritis, ulcerative colitis, and Crohn's disease 2, they are second-line choices in this scenario for several critical reasons:

  • Pregnancy considerations: In a young woman of childbearing age, infliximab and etanercept carry rare associations with VACTERL syndrome (vertebral, anal, cardiovascular, tracheoesophageal, renal, and limb abnormalities) when used during pregnancy 4

  • Loss of efficacy: TNF-α antagonists demonstrate loss of efficacy over time in psoriasis, potentially requiring dose escalation that is often not approved by insurers 4

  • No superior benefit: Since ustekinumab addresses both conditions effectively, there is no clinical advantage to choosing a TNF-α inhibitor first-line 2

IL-17 Inhibitors (Secukinumab, Ixekizumab, Brodalumab)

IL-17 inhibitors are absolutely contraindicated in this patient despite their superior efficacy for psoriasis alone:

  • Secukinumab, ixekizumab, and brodalumab have demonstrated efficacy in psoriasis and psoriatic arthritis but may exacerbate or induce inflammatory bowel disease 2

  • Recent systematic reviews confirm that IL-17 inhibitors have the potential to worsen IBD despite being recognized treatments for psoriasis 6

  • The British Association of Dermatologists specifically warns that secukinumab may increase the risk of IBD events, and therapy should be discontinued if new-onset or worsening IBD occurs 7

IL-23 Inhibitors (Guselkumab, Tildrakizumab)

  • Guselkumab has demonstrated efficacy only in psoriasis, with no established efficacy data for Crohn's disease 2

  • Tildrakizumab similarly lacks FDA approval and efficacy data for inflammatory bowel disease 8

Dosing Protocol for This Patient

Induction Phase (Crohn's Disease Protocol)

  1. Determine weight-based IV dose 1:

    • ≤55 kg: 260 mg (2 vials) IV infusion
    • 55-85 kg: 390 mg (3 vials) IV infusion

    • 85 kg: 520 mg (4 vials) IV infusion

  2. Pre-treatment screening 1:

    • Tuberculosis testing (PPD or IGRA)
    • Screen for active infections
    • Hepatitis B screening
    • Pregnancy test (given patient is a young woman)

Maintenance Phase

  • 90 mg subcutaneous injection 8 weeks after IV induction, then every 8 weeks thereafter 1

  • This every-8-week schedule is specifically for Crohn's disease and differs from the every-12-week schedule used for psoriasis alone 1

  • The more frequent dosing for Crohn's disease will provide adequate coverage for the psoriasis as well 3

Expected Outcomes

For Crohn's Disease

  • Patients with concurrent autoimmune skin disease show better response to ustekinumab than those without, with more complete resolution of moderate/severe intestinal disease 3

  • Clinical trials demonstrate ustekinumab can induce and maintain remission in Crohn's disease 9

  • Expect improvement in inflammatory markers (CRP, fecal calprotectin) and endoscopic findings 3, 9

For Psoriasis

  • Standard ustekinumab dosing achieves PASI 75 response rates of 66.7-75.7% at week 12 8

  • The Crohn's disease dosing protocol (90 mg every 8 weeks) provides more frequent dosing than the standard psoriasis protocol, potentially enhancing psoriasis control 1

Critical Safety Considerations

Infection Risk

  • All biologics targeting IL-12/IL-23 carry warnings about infections, particularly granulomatous infections such as tuberculosis, histoplasmosis, and coccidiomycosis 4

  • Mandatory TB screening before initiation; treat latent TB before starting ustekinumab 1

  • Do not start during any clinically important active infection 1

Pregnancy Planning

  • Ustekinumab is FDA pregnancy category B 4

  • Unlike infliximab and etanercept, ustekinumab has not been associated with VACTERL syndrome 4

  • In a young woman, discuss contraception and pregnancy planning, as ustekinumab has a more favorable pregnancy profile than TNF-α inhibitors 4

Monitoring

  • Monitor for signs of infection throughout therapy 1

  • Assess both Crohn's disease activity (clinical symptoms, inflammatory markers, endoscopy) and psoriasis severity (BSA, PASI) 3, 9

  • Consider discontinuing if serious infection develops 1

Common Pitfalls to Avoid

  1. Do not use psoriasis-only dosing (45 mg every 12 weeks for patients ≤100 kg): This will undertreated the Crohn's disease 1

  2. Do not choose secukinumab despite its superior efficacy for psoriasis alone (79% PASI 90 at week 16): The risk of exacerbating Crohn's disease is unacceptable 10, 7, 2

  3. Do not delay treatment to try topical therapy or phototherapy first: Newly diagnosed small bowel Crohn's disease requires systemic therapy, and ustekinumab addresses both conditions simultaneously 1

  4. Do not use combination biologic therapy: There is no evidence supporting combining ustekinumab with other biologics, and such combinations carry unknown risks 7

References

4
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

7
Guideline

Secukinumab Initiation in Psoriasis

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

8
Guideline

Tildrakizumab vs. Ustekinumab for Moderate-to-Severe Plaque Psoriasis

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

10
Guideline

Monoclonal Agents for Moderate to Severe Psoriasis

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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