© Angel Fernandez Flores, MD, PhD Pityriasis rosea

Pityriasis rosea

 

Cause

Human herpesvirus 6 and 7 have strongly been incriminated in the disease (J Am Acad Dermatol. 2009 Aug;61(2):303-18).

 

Clinical presentation

A herald patch as the initial presenting lesion:

    It is a single erythematous macule (2 to 10 cm)with a fine scale, commonly located on the trunk.

    It evolves with central clearing.

A simmetric"christmas tree" rash, one or two weeks after the herald patch:

    Small pinkish oval macules with peripheral scaly collarettes and central clearing.

Pruritus is present in up to 25 % of cases.

General symptoms of a viral disease, can be evidemced, such as headache, malaise, arthralgias, chills, vomiting, diarrhea or constipation.

 

Morphology

Superficial perivascular inflammatory infiltrate extending to the epidermis.

 

 

The latter shows mild spongiosis, as well as mounds of parakeratosis.

 


Some extravasated hematies can also be seen.

 



Main differentials:

Gyratum erythema: in early stages, pityriasis rosea can be difficult to distinguish. Extravasated hematies are not a feature of gyratum erythema.

Superficial chronic dermatitis (digitate dermatosis): elongated mounds of parakeratosis; spongiosis is even less than in pityriasis rosea.

 

© Angel Fernandez Flores, MD, PhD