Is it psoriasis or eczema? New test provides answers

| Emily Delzell

A new genetic test developed by a group of German researchers may help dermatologists tell psoriasis from eczema, according to a study published in July in Science and Translational Medicine that identified genes specific to each condition.

Psoriasis and eczema are both can cause red, raised patches on the skin, and even experienced dermatologists can have a hard time telling the two apart, especially when the affected skin is on the hands or scalp, said study author Dr. Kilian Eyerich.

The study showed that, while psoriasis and eczema both involve inflammation, the responses of the genes involved in each disease are quite different—and sometimes create opposing reactions. This means treating patients incorrectly can cause problems, Eyerich said.

“Modern therapies for both conditions are so specific they won’t work if the patient is misdiagnosed, and incorrect treatment can even worsen the disease because each condition is driven by distinct, even antagonistic, immune responses,” he said.

Both psoriasis and eczema involve complicated genetic processes that vary greatly from person to person, so pinpointing the specific genes at work in each has been difficult.

It’s rare for one person to have both conditions, but the scientists identified 24 people with psoriasis and eczema. They compared skin samples of psoriasis and eczema from each individuals and with the person’s unaffected skin. This allowed them to cut out a number of genetic variables and identify distinct genetic signatures for psoriasis and eczema, Eyerich said.

The researchers selected two genes identified in the study—one reliably specific to psoriasis, the other to eczema—to create the diagnostic test. They are now simplifying the test so dermatologists can use it easily and quickly in their offices, and Eyerich said it could be available in about a year.

Many of the genes identified in the study as specific to psoriasis regulate metabolic functions, confirming the known link between psoriasis and metabolic syndrome—a cluster of risk factors for cardiovascular disease that includes obesity, high blood sugar and cholesterol.

In contrast, eczema-related genes included those related to the epidermis, the outermost layer of skin cells that acts as a barrier to water loss and infection.

“This study allows a deep insight into what happens in psoriatic skin,” Eyerich said. “While many of the key genes are already targeted by modern therapies, there are additional factors that may lead to even better therapies.”

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