Ultrastructural studies in epidermolysis bullosa hereditaria. IV. Recessive dystrophic types with junctional blistering. (Infantile or Herlitz-Pearson type and adult type).

Recessive dystrophic epidermolysis bullosa with junctional blisters includes both the classical epidermolysis bullosa hereditaria letalis Herlitz (Herlitz-Pearson type) and a recently separated more benign adult type. Ultrastructural examination was performed of 13 skin specimens from 3 cases of the Herlitz-Pearson-type and one case of the adult type. Principal ultrastructural changes in involved, intact and experimentally frictioned skin regions, common to all patients, are as follows: In nonseparated areas hypoplasia of the hemi-desmosomes and mild decrease of the tonofibrils are found. Hypoplasia of hemi-desmosomes consists of a marked rudimentary structure of the sub-basal dense plaque and the attachment plaque. Focal widening of the lamina lucida suggesting early blistering occurs exclusively in the areas devoid of hemidesmosomes. In separated areas cleavage always occurs in the plane of lamina lucida, viz. the mode of blistering is junctional. Fragments of basal cells are often encountered still remaining attached to the blister floor ("epidermolytic torn-off phenomenon"). These torn-off portions of basal cells are characterized by relatively rich distribution of hemidesmosomes. Basal cells forming the blister roof frequently show small gaps of basal plasma membrane and rarefaction of the basal part of the cytoplasm, which are thought to be secondary changes. Among the observed alterations, structural defects of hemidesmosomes are considered to play the most important role in the pathogenesis of junctional blisters.