The disease of which I intend to speak to-day does not belong to those very frequently observed. Its frequency, according to statistics, is between 5 and 12 per cent, of all skin affections presenting themselves for treatment. When we consider that the affection, by not causing imminent symptoms, is apt to be overlooked by the patient, its frequency will be somewhat augmented. If we add to this fact that the discernible features of the disease greatly resemble another skin eruption—tinea maculosa and circinata—we have another source of increased frequency, which must be accounted for when estimating the ratio of its occurrence among the dermatoses.
It is strange that even busy dermatologists will at times encounter no case at all, while at other times the well-known mysterious multiplicity of cases will materialize itself by a string of cases within a limited period. Hyde saw 87 cases in 18 months. The spring
WEISS L. PITYRIASIS ROSEA.AN ERYTHEMATOUS ERUPTION OF INTERNAL ORIGIN.. JAMA. 1903;XLI(1):20-28. doi:10.1001/jama.1903.04470030024006