Phenotype Classification - How does it work?

[Guide]

There are different approaches offered by the various 'authorities' on rosacea diagnosis into phenotypes. [1] However, they all agree that the phenotype classification is superior to the subtype classification (used since 2002) initially proposed by the NRS 'expert' panel. [2] The phenotype classification began in November 2016.

The general consensus is "at least one diagnostic or two major phenotypes are required in order to diagnose a patient with rosacea." [3]

(1) Diagnostic Cutaneous Signs (only one required)

The ROSCO panel list includes persistent centrofacial erythema associated with periodic intensification by potential trigger factors as a minimum diagnostic feature of rosacea and phymatous changes are individually diagnostic of rosacea.

Fixed centrofacial erythema, papules and pustules, flushing or blushing, phymatous changes are included in the NRS panel diagnostic list. 

Dr. Tan with the ROSCO panel, as well as the NRS Panel, and Dr. Del Rosso with the AARS panel both concur that facial erythema is essential to a diagnosis of rosacea. [4]

“Recent developments in rosacea call for clinicians to place greater emphasis on persistent facial erythema, one of the most common and troublesome features of the disorder, now designated as its most prevalent diagnostic phenotype.” [6]

The RRDi concurs that erythema is essential to a diagnosis of rosacea. Usually papules and pustules include erythema and so does phyamtous changes as well as flushing/blushing. 

OR

(2) RRDi Phenotypes (two required)

(1) Flushing
(2) Persistent Erythema
(3) Telangiectasia
(4) Papulopustular (Papules/pustules Lesion Counts)
(5) Phymatous
(6) Ocular Manifestations

Variances in Phenotype Listings
The ROSCO panel has no numbering phenotype system but lists the above phenotypes. [1]

The NRS 'expert' committee's approach has no numbering system and divides four phenotypes with three secondary phenotypes. [1] [5]

Galderma tweets four major phenotypes and four minor phenotypes. [1]

The AAD follows the NRS expert panel recommendations. [1]

The AARS has its own way of acknowledging the phenotype classification into six phenotypes with no numbering system: 

"central facial erythema without papulopustular (PP) lesions;" 
"central facial erythema with PP lesions;" 
"the presence of phymatous changes,"
"ocular signs, and symptoms;" 
"extensive presence of facial telangiectasias;" 
"and marked, persistent, nontransient facial erythema that remains between flares of rosacea and might exhibit severe intermittent flares of acute vasodilation (flushing of rosacea)" [1]

Medscape recognizes four major phenotypes and three secondary phenotypes following the NRS recommendations [1]

Secondary Phenotypes
“The presence of any two of the major phenotypes also may be considered diagnostic, and secondary phenotypes include burning, stinging, edema, and dryness. Rosacea therefore encompasses a multitude of possible combinations of signs and symptoms. ” [6]

Conclusion
The phenotype classification is well established by recognized rosacea authorities and has surpassed the subtype classification. If your physician continues to parrot the subtype classification you may want to refer this page to your physician for his attention. 

End Notes

[1] ROSCOE Panel • NRS Expert Panel • Galderma • AAD • AARS • Medscape

[2] Phenotype Treatment is Superior

[3]  Clinical, Cosmetic and Investigational Dermatology February 2020

[4] Phenotype Classification Uses Signs and Symptoms Better

[5] The four phenotypes the NRS lists are Papules and Pustules, Flushing, Telangiectasia, and  Ocular manifestations. The secondary phenotypes are  Burning or stinging, Edema, and Dry Appearance. 
Standard classification and pathophysiology of rosacea: The 2017 update by the National Rosacea Society Expert Committee. 

[6] Update on Facial Erythema in Rosacea

[Guide]

"Consequently, a schema established on patient features that encompassed the diversity of clinical presentations was proposed by the global ROSacea COnsensus (ROSCO) panel in 2017. This phenotype approach was based on an “individual’s observable characteristics that can be influenced by genetic or environmental factors”. The ROSCO panel represented an international rosacea expert group of dermatologists and ophthalmologists from Asia, Africa, Europe, North America, and South America to ensure global representation. In this paradigm, subsequently endorsed by the National Rosacea Society, two features were independently diagnostic for rosacea. In their absence, the presence of two or more major features can establish the diagnosis. Furthermore, minor features might also present with diagnostic and/or major features (Table 1). The next step was to align the management strategies with the phenotype approach to enable optimization of patient outcomes and improve general well-being by targeting those features most bothersome to the patient."

American Journal of Clinical Dermatology volume 22, pages 457–465 (2021)
Rosacea: New Concepts in Classification and Treatment
Esther J. van Zuuren, Bernd W. M. Arents, Mireille M. D. van der Linden, Sofieke Vermeulen, Zbys Fedorowicz & Jerry Tan