[Pityrosporum ovale in keratotic lesions of seborrheic areas].

The Pityrosporum ovale (PO) is demonstrated in various percentages of the keratotic lesions of the seborrheic areas depending upon the techniques. The accumulation of horny material most probably enhances the multiplication of the yeast and makes its demonstration easier. The PAS technique prevails upon the mycological ones (77 p. 100 versus 50-65 p. 100). PO proliferates only in the keratin layer; there are isolated spores, small clusters or even large stratified colonies. On the other side the prevalence of PO does not differ significantly whatever the ultimate diagnosis of seborrheic keratosis, actinic keratosis, naevocellular nevus or vial wart. Its multiplication within the keratin layer of the lesions does not make any difference as far as the lymphocytic infiltration of the dermis is concerned.