Page:Transactions of the Royal Society of Tropical Medicine and Hygiene, volume 1.djvu/301

Rh Differential Diagnosis.—Erythrasma.—In erythrasma the patches have a fawn or dark reddish colour, with a fine desquamation; the eruption is not limited by a raised red edge, the fungus (Microsporoides minutissimum) is quite different from the fungi found in dhobie itch.

Intertrigo.—Intertrigo is very common in the Tropics, especially in corpulent persons. The lesions are very superficial, have not a festooned contour, and the margin is not sensibly elevated; no fungus is found.

Eczema.—Primary eczema of the scrotum and the skin of the thighs in contact with it, is as frequent in the Tropics as it is in temperate zones. The eczema is generally of the moist variety—the moist surface, the absence of the festooned elevated margin, etc., easily distinguishing it from Tinea cruris. As already stated, however, an eczematous-like dermatitis due to scratching often develops after a time on old dhobie itch lesions.

Prognosis.—The affection, if not energetically treated, has a tendency to become very chronic, and to last for years. Occasionally the eruption spreads to the whole body, forming rings or solid patches : at other times a distressing dermatitis develops on old dhobie itch patches, due to scratching. Tinea cruris may disappear during the cold season or when the patient goes to the hills, to reappear as soon as the hot season commences. During the period of quiescence the skin of the affected regions often shows a brownish discoloration, furfuraceous, somewhat similar to erythrasma.

Treatment.—In tropical practice the usual treatment is a chrysarobin or Goa powder ointment. All the so-called dhobie itch ointments sold as patent medicines contain Goa powder. The result is generally fairly successful. The patient should be informed that the medicine stains the linen, and gives also a dark stain to the skin, and that