Phenotype Treatment is Superior

[Guide]

To understand why phenotype based treatment is superior to subtype based treatment for rosacea, lets take the case of classifying rosacea as Subtype 1 - Erythematotelangiectatic Rosacea. 

A rosacean could present clinical features of erythema without any flushing symptoms and be treated with brimonodine. Another rosacean could present with clinical features of teleangiectasia and be treated with laser. These two very different clinical features are classified into one subtype. 

A third rosacean could present with erythema due to flushing with no telangiectatic signs and treated with anti-flushing drugs. 

The advantage of a phenotype based treatment is that these three clinical features are separated into (1) Phenotype Flushing,  (2) Phenotype Persistent Erythema or (3) Phenotype Telangiectasia and receive totally different treatments determined by this new phenotype based treatment protocol. 

"The characteristic rosacea symptoms manifest primarily, but not exclusively centrofacially, with forehead, nose, chin and cheeks significantly affected. Based on the various main symptoms a classification of the individual clinical pictures can be performed. However, a classification often does not reflect the clinical reality, since the various symptoms commonly coexist. The present review provides an introduction on pathogenesis and clinical manifestations of rosacea and prefers a symptom-oriented therapy approach." [1]

Subtype Classification Overlaps Signs and Symptoms

"However, a classification often does not reflect the clinical reality, since the various symptoms commonly coexist. The present review provides an introduction on pathogenesis and clinical manifestations of rosacea and prefers a symptom-oriented therapy approach." [2]

Since 2002, "A subtype-directed approach to treating rosacea patients is recommended to dermatologists." Wikipedia  The subtype classification has proved wanting and was controversial from the beginning of its inception. 

"Subtyping of rosacea, a post-hoc means of grouping more common presentations, can be and has been subverted inappropriately to imply strict categories without adequate consideration of the varying phenotypic presentation of individuals and the potential for temporal variation." [3]

Phenotype Classification Uses Signs and Symptoms Better

Phenotype Classification Distinguishes Signs and Symptoms

"The panel agreed on phenotype-based treatments for signs and symptoms presenting in individuals with rosacea." [4]

"It’s more important to be categorizing based on patients’ presentation in terms of signs and symptoms,” [5]

"The use of a phenotype approach will allow a more accurate and stringent classification of rosacea. New diagnostic tools emerge, and transcriptome analysis has revealed a possible distinct gene profile for each subtype of rosacea. A change in paradigm towards a phenotype classification, which can also easily be combined with newer diagnostic methods, such as transcriptome analysis, is an interesting possibility. The use of more objective criteria will allow those aspects that are most troubling to patients to be better targeted and allow the best treatment to be selected." [6]

"For past decade, a subtype classification has been used, but now rosacea experts are advising a move toward a phenotype approach which allows better targeting of treatment." [7]

What distinguishes the phenotype classification from the subtype classification? Answer.

Conclusion

Since 2016, a phenotype-directed approach to treating rosacea was introduced by the ROSCO panel which has proved superior and there is no controversy about this since it takes a symptom oriented approach. In December 2018 a group published in the British Journal of Dermatology concluded, "We present the most current evidence for rosacea management based on a phenotype-led approach." [8]

End Notes

[1] Pathogenesis and clinical presentation of rosacea as a key for a symptom-oriented therapy.
J Dtsch Dermatol Ges. 2016 Dec;14 Suppl 6:4-15
Reinholz M, Ruzicka T, Steinhoff M, Schaller M, Gieler U, Schöfer H, Homey B, Lehmann P, Luger TA

[2] J Dtsch Dermatol Ges. 2016 Dec;14 Suppl 6:4-15
Pathogenesis and clinical presentation of rosacea as a key for a symptom-oriented therapy.
Reinholz M, Ruzicka T, Steinhoff M, Schaller M, Gieler U, Schöfer H, Homey B, Lehmann P, Luger TA

"Most current guidelines are based on the identification of the rosacea subtype to select the appropriate therapy. However, in reality there is often an overlap of clinical features across rosacea subtypes in each patient, requiring several therapeutic strategies for optimal outcome. Thus, there is no single best way to treat all rosacea patients."

Dermatoendocrinol. 2017; 9(1): e1361574.
Rosacea: Epidemiology, pathogenesis, and treatment
Barbara M. Rainer, Sewon Kang, and Anna L. Chien

[3] Shortcomings in rosacea diagnosis and classification

[4] Br J Dermatol. 2016 Nov 12. doi: 10.1111/bjd.15173. 
Rosacea treatment update: Recommendations from the global ROSacea COnsensus (ROSCO) panel.
Schaller M, Almeida L, Bewley A, Cribier B, Dlova N, Kautz G, Mannis M, Oon H, Rajagopalan M, Steinhoff M, Thiboutot D, Troielli P, Webster G, Wu Y, van Zuuren E, Tan J.

[5] Phenotype Classification Uses Signs and Symptoms Better

[6] Forum for Nord Derm Ven 2017, Vol. 22, No. 1
Rosacea: Time for a New Approach • Rosacea-Time-for-a-New-Approach.pdf
CARSTEN SAUER MIKKELSEN, PETER BJERRING, MARGARETA LIRVALL, MARGARETA SVENSSON, HELENE RINGE HOLMGREN, ALEXANDER SALAVA AND THEIS HULDT-NYSTRØM

]7] J Drugs Dermatol. 2019 Sep 01;18(9):888-894
Recognizing Rosacea: Tips on Differential Diagnosis
Johnson SM, Berg A, Barr C

[8] Br J Dermatol. 2018 Dec 26. doi: 10.1111/bjd.17590. [Epub ahead of print]
Interventions for rosacea based on the phenotype approach: an updated systematic review including GRADE assessments.
van Zuuren EJ, Fedorowicz Z, Tan J, van der Linden MMD, Arents BWM, Carter B, Charland L.

[Guide]

"However, shortcomings in these diagnostic criteria and subtyping have become apparent. This includes the lack of specificity of some primary features (flushing, papules/pustules, telangiectasia), the exclusion of phyma as a primary feature and the conflation of multiple features into subtypes. For example, the erythematotelangiectatic subtype comprises flushing and persistent central facial erythema with or without telangiectasia, whereas the papulopustular subtype comprises persistent central facial erythema with transient, central facial papules and/or pustules. Thus, both have persistent central facial erythema as a common feature. This has led to confusion in epidemiological research whereby some studies consider them as separate categories, while others aggregate all with central facial erythema as erythematotelangiectatic, a subgroup of which is papulopustular. Furthermore, it does not account for patients presenting with a solitary diagnostic criterion and absence of the others defining a specific subtype. For example, how would one classify a patient with persistent central facial erythema alone but without flushing and telangiectasia? In addition, severity determination of subtypes is complicated by the presence of multiple features each of which may vary in individual severity and responsivity to intervention. However, these individual features were not previously typically evaluated separately. Furthermore, in clinical practice, subtyping may inadequately capture the signs and symptoms of individual patients as some features can extend across subtypes.

Consequently, revised diagnostic criteria have been proposed and recommendations made to abandon the subtyping approach."

Br J Dermatol. 2019 Jul;181(1):65-79.  doi: 10.1111/bjd.17590.  Epub 2019 Mar 10. Pubmed
Interventions for rosacea based on the phenotype approach: an updated systematic review including GRADE assessments
E J van Zuuren, Z Fedorowic, J Tan, M M D van der Linden, B W M Arents, B Carter, L Charland