There are no consistently abnormal laboratory findings in the case of rosacea, such that blood tests are normally not necessary for diagnosis. The pustules are usually sterile, therefore bacterial cultures can mostly be dispensed with. If desquamation is present, a fungal infection should be excluded. Eye involvement is common and requires an ophthalmologic examination. Despite its high incidence, a well-established nosology of rosacea is still lacking. The term “rosacea” has been applied to patients with a diverse set of clinical findings that may or may not be an integral part of this disorder. [1] In order to simplify the diagnosis of the disease, the U.S. National Rosacea Society has developed a standard classification system(http://www.rosacea.org/class/index.html).[1] This is based on the primary features of rosacea and defines four subtypes plus one variant form (for description of subtypes and clinical images see rosacea.dermis.net). Regardless of subtype, however, each individual case may worsen from mild to moderate to severe stages of the disease. Early diagnosis and treatment are thus essential to prevent this progression.

Primary features

Rosacea typically affects the convexities of the central face. According to the National Rosacea Society Expert Committee on the Classification and Staging of Rosacea, the presence of one or more of the following primary features is indicative of rosacea: [1]

• Flushing (transient erythema)
• Nontransient erythema
• Papules and pustules
• Telangiectasia

These signs may occur very different in intensity and appearance. It is very common, that patients display more than one of these diagnostic features.

Secondary features

The following signs and symptoms often occur with one or more of the primary features of rosacea above. However, in some patients they can occur independently: [1]

• Burning or stinging
• Plaque
• Dry appearance
• Edema
• Ocular manifestations
• Peripheral location

Differential diagnosis

In subtype or stage 1 rosacea the main differential diagnoses to consider are:

• Carcinoid syndrome
• Allergic contact dermatitis
• Angioedema
• Mastocytosis and
• Lupus erythematosus

The most common differential diagnoses of subtype or stage 2 rosacea are:

• Acne vulgaris

In subtype or stage 3 rosacea the main differential diagnoses are:

• Nodulate/conglobate acne (Acne conglobata)
• Leonine facies of leprosy
• Leukemia
• Melkersson-Rosenthal syndrome
• Acromegaly
  This particularly applies once rhinophyma has developed.

For further information see

• Rosacea subtypes and variants
• Diagnosis of rosacea

References

[1] Wilkin J, Dahl M, Detmar M, Drake L, Feinstein A, Odom R, Powell F. Standard classification of rosacea: Report of the National Rosacea Society Expert Committee on the Classification and Staging of Rosacea. J Am Acad Dermatol 2002;46:584-7.