Research has identified a single gene biomarker that can distinguish atopic dermatitis (AD) and psoriasis with 100 percent accuracy; the presence of nitride oxide synthase 2 (NOS2) in psoriatic skin can be identified non-invasively using adhesive tape strips.

Results of a study recently published in Journal of Allergy and Clinical Immunology confirm the validity of the psoriasis biomarker.1 The study involved 20 adults with moderate to severe AD, 20 with moderate to severe psoriasis, and 20 healthy individuals. Tape strip samples were collected from each individual, from lesionial as well as clinically unaffected skin. In addition to identifying the unique presence of NOS2 in psoriasis, the study analyzed other genetic markers identified from the tape strip tests. Not surprisingly, tape strips from AD patients strongly expressed cell markers related to T-helper 2 (Th2) immune response, while psoriasis patients displayed higher levels of Th1 and Th17 cytokines.

Of note, and consistent with some previous research, the study found that in AD, compared to psoriasis, nonlesional tape-stripped skin was more similar to lesional skin.

Implications for Care

The ability to definitively diagnose atopic dermatitis or psoriasis with a non-surgical technique is a welcome development from a clinical perspective. Similar tape strip-based diagnostic tools are already available for melanoma, so the dermatology community is familiar with the concept.

While the vast majority of inflammatory skin diseases can be diagnosed based on visual assessment and patient-reported symptoms, there are cases that may stymie clinicians. Consider that the hallmarks of both psoriasis and atopic dermatitis are itch and erythema.

Traditionally, indeterminate cases of psoriasis or eczema or a mixed presentation would warrant skin biopsy. But biopsies can be painful and present a low but notable risk for infection and scarring. Unfortunately, and perhaps most importantly, biopsies are not always definitive.

When the tape strip test becomes commercially available, it may prove especially useful for those children and adolescents who have indeterminate disease or perhaps have a history of eczema and are developing new-onset psoriasis. Those individuals who develop psoriasis at an early age are at higher risk for developing joint disease or psoriatic arthritis, so the ability to identify and treat these patients as early as possible is important.

There have been a few case reports of patients treated with dupilumab for atopic dermatitis who have developed psoriasis.2,3 Theoretically, this is thought to result from a shift in the cytokines from one channel that drives atopic dermatitis to a second channel that causes psoriasis. It would be interesting to have a baseline non-invasive tape strip test to confirm atopic dermatitis at the onset of therapy and it would be invaluable to document a shift in the genetic makeup of the skin barrier via tape strip if a patient did convert to psoriasis.

A Timely Discovery

The identification of this unique genetic marker for psoriasis comes at an important time for the specialty. The treatment landscape continues to expand, with safe, effective, and specific treatments for both psoriasis and atopic dermatitis currently available and in the pipeline. No longer are we forced to use the same non-targeted therapies for all inflammatory diseases. With a definitive diagnosis of atopic dermatitis or psoriasis, we can select the most appropriate therapy—including perhaps a targeted biologic—to manage each individual’s disease.

Thoughts on “Adequate Control”

Even in 2020, with so many very highly effective biologic agents available to treat psoriasis and now atopic dermatitis, it is really disappointing to know that some patients will walk into a dermatology office and not be offered adequate treatment for their disease.

In many cases, the amount of paperwork needed to justify a biologic therapy for psoriasis can be a deterrent to prescribing. In the case of psoriasis, lingering misunderstanding of the actual pathophysiology of the disease may play a role. We now clearly know that atopic dermatitis and psoriasis represent systemic diseases. The lesions on the skin are manifestations of the systemic inflammatory process. Therefore, it is unreasonable to treat patients with significant skin involvement with topical creams, lotions, or foam preparations.

It is not practical for patients to go through elaborate topical medication application routines twice daily to try to achieve “satisfactory” results. Those who are able to follow the routine may require upward of 20 to 30 minutes twice a day just to get their medication on. In doing so, they still may not achieve adequate control.

1. He H, Bissonnette R, Wu J, et al. Tape strips detect distinct immune and barrier profiles in atopic dermatitis and psoriasis [published online ahead of print, 2020 Jul 9]. J Allergy Clin Immunol. 2020;S0091-6749(20)30824-1.

2 D’Ambra I, Babino G, Fulgione E, et al. Psoriasis onset under dupilumab treatment in two patients affected by Atopic Dermatitis and one patient affected by Alopecia Areata: clinical and dermoscopic patterns [published online ahead of print, 2020 Aug 10]. Dermatol Ther. 2020;e14169.

3. Kim HS, Yeung J. Psoriasis appearing after dupilumab therapy in atopic dermatitis: A case report. SAGE Open Med Case Rep. 2020;8:2050313X20940458. Published 2020 Jul 10.