Ultrastructure of dyskeratosis in morbus Darier

Biospy specimens from three patients with morbus Darier were studied by electron microscopy: Grains appeared in groups in the midst of dyskeratotic lesions and were recognized as being the result of more advanced acantholysis and precocious keratinization. Corps ronds were formed individually in the regions lateral to that of grains, where hypergranulosis was prominent in contrast to a mild dyskeratosis. Therefore, the formation of grains and corps ronds seem to be independent of each other. While in the literature acantholysis has mainly been ascribed to the separat;on of desmosones into two segments, another initial process seems to be the primary disappearance of the attachment plaque along with the connecting tonofilaments. From the existence of the other contact complexes, it seems likely that a restoration of desmosomes between acantholytic cells should take place. In early stages of dyskeratotic cells, keratinosomes were increased in number and some of them persisted inside the plasma membrane without a release into the intercellular spaces, and thus they were present in grains and corps ronds. The dyskeratosis in morbus Darier is characterized by a premature, incomplete and individual keratinization as evidenced by the existence of keratohyalin granules and keratinosomes as early as at the level of the 3rd epidermal layer and the absence of a keratin pattern in the dyskeratotic horny cells.