PITYRIASIS ROSEA

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**Synonyms:** Pityriasis maculata et circinata; Herpes tonsurans maculosus.

Pityriasis rosea is an acute mildly inflammatory disease of the skin characterized by an eruption of small, rose-red, slightly elevated macules, many of which slowly increase to coin-sized round or oval patches. After a lesion has attained a diameter of about half an inch its central portion becomes dull yellow or salmon colored, while the slightly elevated border remains a brighter red. The epidermis over the yellowish middle part is dry and shiny and crinkles easily when the patch is subjected to slight lateral compression. There is nearly always a fine furfuraceous desquamation from the surface of the lesion, more marked toward the periphery. Not infrequently a collar of small gray scales remains attached just at the junction of the yellowish center and the pink border. Large macules often clear up entirely in the middle. Contiguous lesions may coalesce and form irregularly outlined patches in which the fused borders sometimes, though rarely, form reticulated patterns. Most of the lesions cease to increase in diameter in about a week, some much sooner; they do not all reach the same stage of development. New lesions continue to appear, rapidly for a few days or more slowly for a couple of weeks. The lesions are exceedingly superficial and there is rarely any palpable infiltration of the skin, though efflorescences located in warm, moist regions, as in the axillae, beneath the hanging breasts or about the genitals, may become somewhat thickened, but never abraded or covered with necrotic membranes. The usual distribution of the rash is upon the trunk; that is, upon the chest, back and shoulders, and especially on the sides of the thorax and about the clavicles. Lesions are not infrequently present upon the neck, arms and thighs, but they rarely appear upon the face, scalp, hands

or below the knees. On the back and sides of the chest the oval lesions are often roughly arranged in series along the course of the ribs, with their long axes inclined in the same direction. Occasionally, but by no means in every case, there occurs a fairly large primary efflorescence, a so-called herald spot, upon some part of the body, usually on the trunk, which is followed in four to twelve days by the general eruption. The rash persists for three to six weeks or longer, acquiring gradually a more brownish tinge. The affection sometimes causes a moderate amount of itching, but usually only when the skin is moist with perspiration. There are no other subjective symptoms. The disease occurs predominantly among young individuals and is rare in the aged. The cause is unknown. **DIAGNOSIS:** The pink ring lesions with the salmon-colored parchment-like centers are almost pathognomonic. In *syphilis maculosa*, *papulo-squamosa* or *circinata* the efflorescences are frequently present on the hands or face and are of a more uniform size and a less bright red color and are nearly always associated with other manifestations of syphilis. *Psoriasis* has a different distribution and its scales are larger and far more plentiful. *Eczema seborrhoicum* is a chronic disease; the lesions, when numerous on the body, are present also on the scalp and usually on the face. The sternal and interscapular regions are particularly affected. The scales are thick and greasy. *Trichophytosis corporis* does not spread so rapidly nor over such wide areas and the fungus can be found easily with the microscope. **TREATMENT:** Pityriasis rosea recovers spontaneously and treatment does not seem to have any marked effect. A 4 to 8 per cent sulphur ointment is usually prescribed. A 1 per cent carbolic acid lotion may be used to allay the itching.

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