Precocious appearance of involucrin and epidermal transglutaminase during differentiation of psoriatic skin.

We compared the distribution in psoriatic skin of three different markers usually found in the stratum granulosum of normal skin. Using dansylcadaverine, we demonstrate that epidermal transglutaminase activity can be detected in most of the suprabasal layers of involved psoriatic skin and that the epidermal transglutaminase activity closely matches involucrin distribution. The glycoprotein GP37 was not detected in involved psoriatic skin of stable lesions. These results suggest that the integrated control of several independent pathways of terminal differentiation is lost in psoriasis, resulting in the classical feature of parakeratosis with absence of the stratum granulosum.