When a psoriasis patient stops responding to treatment, the instinct is often to escalate or switch biologics — but experts say that's frequently the wrong move. At Brazil's 79th Congress of Dermatology, dermatologists emphasized that the first critical step is distinguishing primary failure (never achieving a meaningful response) from secondary failure (losing a response that was once achieved), as each demands a different clinical path.

A major theme was the prevalence of "false failures." Poor adherence, underdosing, dispensing interruptions, and misdiagnosis can all mimic true treatment resistance. Conditions like dermatophytosis, nummular eczema, and mycosis fungoides can look like resistant psoriatic plaques, while structural joint damage in psoriatic arthritis can be mistaken for ongoing inflammation.

Key Takeaways:

• A Brazilian study of 166 biologic users found that supply chain issues — not patient behavior — increased discontinuation risk by 45%
• Antidrug antibody testing is most useful in secondary loss of response, not as a routine pre-treatment screen
• Deucravacitinib, a new oral TYK2 inhibitor, showed durable responses over 104 weeks in a Japanese cohort, though it doesn't yet outperform IL-17 or IL-23 inhibitors for skin clearance
• Switching drug classes can restore control: 82.6% of patients achieved PASI-75 after switching from an IL-23 to an IL-17 inhibitor

Why it matters: Misreading a logistical or diagnostic problem as pharmacologic failure can lead to unnecessary treatment intensification — and missed opportunities to address the real issue. A structured, stepwise evaluation protects patients and preserves future treatment options.