ICHTHYOSIS BULLOSA OF SIEMENS IS CAUSED BY MUTATIONS IN THE KERATIN 2E GENE

Ichthyosis bullosa of Siemens is a blistering disorder with autosomal dominant inheritance. The disease resembles bullous congenital ichthyo siform erythroderma but is less severe. Keratins K1 and K10 have been implicated in bullous congenital ichthyosiform erythroderma. Linkage a nalysis pointed to the involvement of a keratin type II gene (12q11-13 ) in ichthyosis bullosa of Siemens. Mutations in the highly conserved regions of K1, a member of the type II gene cluster, were excluded. Th e gene coding for keratin 2e is also located in the type II gene clust er and the expression of the gene coincides with the occurrence of epi dermolytic hyperkeratosis. Sequence analysis revealed the presence of mutations in the K2e gene in patients with ichthyosis bullosa of Sieme ns. Three different mutations were detected, one in the 1A domain and two in the 2B domain of the rod. Furthermore, histologic and ultrastru ctural examination of skin biopsies indicated that ichthyosis exfoliat iva is identical to ichthyosis bullosa of Siemens. This was confirmed by the results of the molecular analysis. In the family diagnosed as i chthyosis exfoliativa, a mutation was detected that was identical to t he mutation found in one of the families with ichthyosis bullosa of Si emens.