When this skin disease is introduced into a country with high relative humidity and fairly uniform temperature, between 80° and 90°F. it spreads with great rapidity.
A dry climate or one showing considerable variations in temperature is not favorable for its spread.
Symptomatology
Fig. 129.—Tinea imbricata from the South Seas. (After Kramen; from Mense.)
The clinical characteristic of this form of ringworm is the presence of rosette-like lesions of several concentric circles of shingle-like, papery scales which are fixed peripherally and free toward the center, thus, from its imbrications, suggesting the name given it by Manson.
If one passes the finger over the affected surface from without inward there is no sensation of roughness but if passed from the center outward the free borders of scales cause a sensation of roughness.
As these circles extend peripherally they meet the peripheral rings of other circles so that various curves appear which give the general appearance of watered silk.
The flaky scales are of tissue paper thinness and are of a dirty, brownish-gray color.
The general health of the patient is not affected but the itching is very severe.