Fine structure of the intercellular space of psoriatic epidermis during retinoid (RO 10-9359) and retinoid-PUVA treatment.

The enlarged intercellular space in the lower malpighian layers of untreated psoriasis contains a fine granular and a coarse granular substance. Both types of this substance increase in amount during 2-6 weeks of retinoid (RO 10-9359) therapy. Retinoid stimulates the formation of these substances, which previously have been termed "mucus". After glutaraldehyde-osmium tetroxide fixation their mucoid nature cannot be ascertained more specific cytochemical techniques being needed for this. A darker, more homogeneous substance in the upper spinous intercellular spaces increases in amount during retinoid therapy. Large amounts of keratinosome-derived lamellae are observed at the boundary of the stratum intermedium and the stratum corneum. Even after 14 weeks of treatment with retinoid or retinoid plus PUVA, at clinical remission, the histological and electron microscopical pictures still show some psoriatic changes, i.e. enlarged intercellular spaces with fine or coarse granular substance.