Pityriasis Veesicolor: A Clinical and Mycological Investigation

SUMMARY. Twenty‐five patients with pityriasis versicolor have been studied clinically and mycologically and the hospital records of a further 62 patients have been analysed. The sex ratio for the whole series was 3 males to 2 females, the age of onset was usually in the early twenties. Nearly all cases in the Cambridge area start in the warmer months of the year. Conjugal cases are reported but a genetic factor in susceptibility is also accepted. Attention is drawn to the extent of the lesions on the limbs and flexural involvement in association with excessive sweating is shown to be common. Pityrosporum orbiculare was cultured from the lesions of 25 of 27 patients and its presence was also detected on uninvolved skin. The evidence for the identity of P. orbiculare and Malassezia furfur is reviewed briefly and the analogy is drawn with yeast/mycelium transition in candidiasis. The ecology of P. orbiculare/M. furfur in pityriasis versicolor is discussed in the light of the results presented.