Pityriasis Rosea
David L. Hall, MD
Tammie Ferringer, MD
Key Facts
Terminology
Common, self-limited, acute papulosquamous eruption of salmon-pink, oval lesions on the trunk, neck, and proximal extremities
Clinical Issues
“Herald patch” with numerous smaller (1-2 cm) pink or salmon-colored round-oval papules with characteristic collarette of scale in “fir” or “Christmas tree” distribution
Microscopic Pathology
Histopathological features are nonspecific
Focal spongiosis, patchy or diffuse parakeratosis, often forming angulated mounds
Mild lymphohistiocytic perivascular and interstitial infiltrate in superficial dermis
Red blood cell extravasation in upper dermis and often epidermis
 Classic distribution of PR shows small, pink or salmon-colored oval papules on the posterior trunk and proximal arms. The long axes of the oval papules follow skin tension lines, forming a “Christmas tree” pattern. |
 “Herald patch”  on the abdomen is surrounded by the typical scaling papules  of the generalized eruptive stage of pityriasis rosea. |
TERMINOLOGY
Abbreviations
Pityriasis rosea (PR)
Synonyms
Pityriasis rosea Gibert
Definitions
Common, self-limited, acute papulosquamous eruption of salmon-pink, oval lesions on the trunk, neck, and proximal extremities
ETIOLOGY/PATHOGENESIS
Unknown
Infectious etiology suspected
Supported by clustering of cases in communal living, history of preceding upper respiratory infection, and low frequency of recurrence
Recent focus on human herpesvirus (HHV)7 and HHV6
PR-like reaction reported with graft vs. host reaction, bone marrow transplantation, acute myeloid leukemia (AML), and Hodgkin disease
CLINICAL ISSUES
Epidemiology
