When a new phenotype approach to the diagnosis of rosacea was proposed 2 years ago, this simpler and more accurate method was accompanied by several corollary advantages, including a more rational approach to treatment and better methods of measuring treatment efficacy, according to an expert speaking at the annual Coastal Dermatology Symposium, held virtually.

“By looking at rosacea in a more simple way – but a more accurate way – we are able to track what happens [to key features] over time,” explained Jerry Tan, MD, of the University of Western Ontario, London.

The newer method of diagnosing rosacea, which relies on phenotyping rather than subtyping, focuses on symptoms and their clinical impact. With the previous method of subtyping, many rosacea patients failed to fit neatly into any of the four categories, producing confusion and diverting attention from troublesome symptoms.

“Rosacea patients often present with a range of features that span multiple subtypes or progress between them,” Dr. Tan explained. The risk is not just a delay in diagnosis but a failure to focus on symptoms patients find most bothersome.

The previous diagnostic criteria for rosacea, published in 2002, identified primary and secondary symptoms within its four subtypes. The new diagnostic criteria, endorsed by the National Rosacea Society and published in 2018, rely on phenotypes defined by diagnostic, major, and minor symptoms. Rather than the four previous subtypes, which were erythematotelangiectatic, papulopustular, phymatous, and ocular, the phenotypes facilitate diagnosis in patients with mixed features.

By replacing “the old thought process of subtyping” with a newer focus on phenotypes, the updated criteria were “aimed toward accuracy, simplicity and practicality,” Dr. Tan said.

Moreover, without squeezing patients into subgroups where they do not neatly fit, the new criteria draw attention to the specific symptoms that bring patients to the clinician.

The phenotype approach to treatment strategies was reflected in a systematic review of treatments based on phenotypes that was published in 2019, not long after the new classification system became available. In this review, coauthored by Dr. Tan, the GRADE certainty-of-evidence approach was employed to identify effective therapies, matching specific symptoms with specific therapies such as low-dose isotretinoin for papules or omega-3 fatty acids for dry eyes.

Based on a patient-centric approach that emphasizes control of key symptoms, Dr. Tan also described a method of documenting the severity of major and minor symptoms at each visit. With this method, called a rosacea patient tracker, patients and physicians can determine whether therapies are effective against the signs and symptoms of disease that they find most burdensome, according to Dr. Tan, who was the first author of an article he cited as a reference to this phenotype-based methodology.

Overall, the phenotype approach to rosacea “rationalizes treatment,” he said.

Specifically, the heterogeneity of symptoms in rosacea is mirrored in the heterogeneity of underlying pathophysiology. According to Dr. Tan, the upregulation of cytokines for inflammation, of angiogenic pathways for vascular symptoms, and of matrix metalloproteinases for tissue remodeling are all implicated in rosacea but drive different types of symptoms. While appropriate skin care and efforts to identify and minimize symptom triggers is appropriate for all patients, phenotypes provide a guide to the most appropriate therapies.

He said he hopes that the focus on phenotypes will draw attention to differences in these pathophysiological mechanisms. According to Dr. Tan, evaluating rosacea from the perspective of phenotypes has represented an important paradigm shift that extends beyond diagnosis.

“The move to the phenotype approach is hopefully simpler, more accurate, and more relevant,” Dr. Tan said.

This same approach has been advocated by others, including Esther J. van Zurren, MD, professor of dermatology at Leiden University Medical Centre in the Netherlands, the lead author of the 2018 systematic review article discussed by Dr. Tan. In this review article on the phenotype approach, specific strategies were recommended for specific symptoms on the basis of grading by an international group of experts that included Dr. Tan, a coauthor.

“These strategies should be directed toward achieving improvements in general well-being by targeting those aspects most bothersome to the patient,” the article advises. Like Dr. Tan, she considers this phenotype-based approach to diagnosis and treatment to be a meaningful clinical advance over the guidelines published in 2002.

“Management strategies for people with rosacea should include phenotype-based treatments,” she agreed, adding that specific choices should be made on the basis of these phenotypes “instead of the previous subtype classification.”

The meeting was jointly presented by the University of Louisville and Global Academy for Medical Education. This publication and Global Academy for Medical Education are owned by the same parent company.