Pityriasis rosea is a disease of unknown origin, but of well defined course and symptoms, and for these and other reasons should be accounted a true morbid entity. It usually begins as a single, light red, scaly patch called the primitive or herald patch, which generally appears on the trunk, on the neck or on the limbs near the trunk. In a short time, this is followed by a vast number of similar but smaller patches, also scattered over the trunk and upper part of the limbs, fequently with a tendency to be more abundant about the primitive patch as if they spread from it. These patches enlarge peripherally, and as they do the center becomes buff colored and finely wrinkled, resembling the wrinkles in cigaret paper. From their incipiency, the patches have a fluffy desquamation, an important diagnostic point, as between these and the roseola of syphilis, which although
MONTGOMERY DW, CULVER GD. PITYRIASIS ROSEATWO UNUSUAL CASES. Arch Derm Syphilol. 1925;12(2):257–260. doi:10.1001/archderm.1925.02370080101009
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