Dupixent Side Effects: What Patients Should Know About CTCL and T-Cell Lymphoma Concerns

Commonly Reported Dupixent Side Effects

The safety profile of Dupixent varies somewhat depending on the condition being treated. Reported adverse effects can include injection-site reactions, eye-related problems such as conjunctivitis or keratitis, and other treatment-specific reactions.

Patients should review the current prescribing information and discuss new or worsening symptoms with their treating healthcare professionals.

This page focuses on a narrower issue that has received growing attention in medical literature: the diagnosis or progression of CTCL in some patients who received dupilumab.

What Is CTCL?

Cutaneous T-cell lymphoma is a group of uncommon lymphomas involving malignant T cells that primarily affect the skin.

Two of the best-known forms are:

• Mycosis fungoides (MF)
• Sézary syndrome (SS)

One reason CTCL can be difficult to recognize is that early disease may resemble common inflammatory skin conditions, including eczema or atopic dermatitis.

That diagnostic overlap is especially important in the Dupixent context because dupilumab is frequently prescribed for atopic dermatitis. For more background, see Dupixent & CTCL.

Why Are Doctors and Researchers Studying Dupixent and CTCL?

Published case reports, case series, retrospective studies, and systematic reviews have described patients who were diagnosed with CTCL during or after dupilumab treatment.

A 2025 systematic review found that the available literature included reports of both newly recognized CTCL and worsening disease following dupilumab treatment, but emphasized that the evidence remains limited by small studies, inconsistent follow-up, and difficulty proving causation. Review the 2025 systematic review on PubMed.

A separate retrospective cohort study found an association between dupilumab use in patients with atopic dermatitis and a higher observed rate of CTCL. The authors also cautioned that an observed association does not establish that dupilumab caused CTCL. Review the retrospective cohort study on PubMed.

More recent clinical reviews and expert recommendations describe the relationship as complex. One major concern is that early CTCL may initially be diagnosed as atopic dermatitis, meaning dupilumab may sometimes be given before the underlying lymphoma is recognized. Some experts have also proposed that changes in immune signaling during dupilumab treatment could potentially unmask or worsen pre-existing malignant T-cell clones in susceptible patients. Review the clinical recommendations on PubMed.

When Might a CTCL Evaluation Be Considered?

Medical evaluation may be especially important when skin disease behaves differently from expected atopic dermatitis.

Recent expert guidance emphasizes diagnostic vigilance in patients with atypical or treatment-refractory disease, particularly adult-onset dermatitis without a typical atopic history. Evaluation may include skin biopsy, clinicopathologic correlation, and, when appropriate, testing for T-cell clonality. Review the diagnostic guidance on PubMed.

Examples of circumstances that may prompt additional evaluation can include:

• persistent or worsening skin lesions despite treatment;
• changes in the character or distribution of a rash;
• unusual plaques, patches, or widespread redness;
• symptoms that do not behave like previously diagnosed eczema;
• a later biopsy showing CTCL, mycosis fungoides, Sézary syndrome, or another T-cell lymphoma.

These findings do not establish a drug-related injury, but they may affect both medical evaluation and any later legal review.

Why the Timing of Diagnosis Matters

For patients who were prescribed Dupixent and later diagnosed with CTCL or another T-cell lymphoma, the medical timeline can be important.

A focused review may look at:

• the original diagnosis that led to Dupixent treatment;
• when Dupixent was first prescribed;
• how long treatment continued;
• whether symptoms improved, remained unchanged, or worsened;
• when biopsies were performed;
• pathology findings;
• when CTCL or another T-cell lymphoma was first formally diagnosed;
• whether earlier skin findings were later reconsidered in light of the lymphoma diagnosis.

Published literature has reported CTCL diagnoses at varying intervals after dupilumab initiation. Earlier systematic reviews described diagnoses occurring within months in some reported cases, while later studies have documented a wider range of timelines. Review the timeline literature on PubMed.

What Records May Matter in a Dupixent CTCL Review?

If someone used Dupixent and was later diagnosed with CTCL or a related T-cell lymphoma, useful records may include:

• Dupixent prescription and pharmacy records;
• dermatology records from before and during treatment;
• photographs of skin findings;
• biopsy and pathology reports;
• immunohistochemistry results;
• T-cell receptor clonality testing, if performed;
• oncology or hematology records;
• dates of diagnosis and treatment;
• records showing how the condition was diagnosed before Dupixent was prescribed.

The significance of any individual record depends on the facts of the case. The site also has a focused resource on records that may matter in a Dupixent CTCL review.

Dupixent Side Effects and Current Litigation

Legal claims involving Dupixent and CTCL are still developing.

The existence of litigation does not establish that Dupixent causes CTCL, and not every patient who develops CTCL after receiving Dupixent will have a viable legal claim.

Current case reviews generally focus on a narrower factual pattern: Dupixent exposure followed by a documented diagnosis of CTCL or a related T-cell lymphoma, together with the patient’s dermatologic and pathology history.

For current procedural information, see the Dupixent lawsuit overview and Dupixent litigation updates.