Junctional epidermolysis bullosa inversa is an autosomal recessive blistering skin disease with an ultrastructural hemidesmosome defect similar to that of the Herlitz disease, yet with a non-lethal and different course of the disease. Its delineation is based on five geographically associated Norwegian families where all parents are likely to carry a mutant EBR2A allele identical in descent. Three informative families show a lod score of +1.65 at zero recombination to a trinucleotide repeat marker in intron 20 of the laminin gamma 1 (LAMC1, previously LAMB2) locus on 1q31. The four patients of these families are all homozygous for the 146 bp LAMC1 allele present only on 5% of random Norwegian chromosomes. The daughter of a deceased patient in a fourth family carries the same 146 bp allele. This extreme association confirms that the disease locus, EBR2A, is at or closely linked to LAMC1. Localized and generalized Mitis types as well as the majority of tested families with the Herlitz type of junctional epidermolysis bullosa appeared not to be similarly linked or associated to LAMC1. The MspI and AluI RFLPs of LAMC1 showed absolute allelic association. Each of the two RFLP haplotypes showed association to either 'long' or 'short' intron 20 STR alleles.
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 separation of des‐mosones 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.
