Disruption of the suprabasal keratin network by mutation M150T in the helix initiation motif of keratin 10 does not affect cornified cell envelope formation in human epidermis

Intermediate Filaments and the Plasma Membrane

A variety of intermediate filament (IF) types show intricate association with plasma membrane proteins, including receptors and adhesion molecules. The molecular basis of linkage of IFs to desmosomes at sites of cell-cell interaction and hemidesmosomes at sites of cell-matrix adhesion has been elucidated and involves IF-associated proteins. However, IFs also interact with focal adhesions and cell-surface molecules, including dystroglycan. Through such membrane interactions, it is well accepted that IFs play important roles in the establishment and maintenance of tissue integrity. However, by organizing cell-surface complexes, IFs likely regulate, albeit indirectly, signaling pathways that are key to tissue homeostasis and repair.

Ichthyosis bullosa of Siemens: its correct diagnosis facilitated by molecular genetic testing

Ichthyosis bullosa of Siemens (IBS, MIM 146800) is a unique congenital ichthyosis characterized by mild epidermal hyperkeratosis over flexural areas, blister formation and the development of superficially denuded areas of hyperkeratotic skin. It is clinically difficult to distinguish severe IBS from mild bullous congenital ichthyosiform erythroderma (BCIE, MIM 113800). In the current literature, 19 IBS families with keratin 2e (K2e) mutations have been reported, despite only five IBS families having been reported before the first identification of K2e mutation in 1994. We studied four patients from three Japanese IBS families. They had previously been misdiagnosed as having BCIE before the correct diagnosis was made after mutation detection. To detect the pathogenic mutations, we performed direct sequencing of the entire coding regions of KRT2E encoding K2e in the patients and healthy family members. K2e mutations, a 1469T-->C transition (L490P) and a 1477G-->A transition (E493K) within the conserved 2B helix termination motif of the rod domain were detected in the families and the definite diagnosis of IBS was made in the four cases. The present results indicate that IBS is not such a rare entity as was previously thought, and accurate diagnosis is now available by mutation analysis.

Stratum corneum hydration and flexibility are useful parameters to indicate clinical severity of congenital ichthyosis

To determine any correlation between the stratum corneum barrier function and the phenotypic severity of congenital ichthyosis, we studied stratum corneum hydration, flexibility, thickness and transepidermal water loss (TEWL) in patients with congenital ichthyosis. Seven patients with congenital ichthyosis aged 2-46 years and age-matched controls were included in the present study. We divided seven patients into two groups; patients with non-bullous type (non-bullous congenital ichthyosiform erythroderma patients) and patients with the bullous type of congenital ichthyosis (bullous congenital ichthyosiform erythroderma and ichthyosis bullosa of Siemens). Stratum corneum hydration, thickness and flexibility were measured using a Corneometer ASA-M2. The stratum corneum thickness was also examined using a skin biopsy technique. TEWL was measured using Evaporimeter AS-TW1. The clinical severity of ichthyosis phenotype was evaluated using a visual analogue scale (VAS). Stratum corneum hydration and flexibility were significantly reduced in both congenital ichthyosis patient groups. Stratum corneum thickness was significantly increased in both groups. In the patient group with non-bullous congenital ichthyosis, significant negative correlations were confirmed between the VAS score and stratum corneum hydration and between the VAS score and flexibility. A significant, positive correlation was also observed between the VAS score and stratum corneum thickness. There was a positive correlation between the VAS score and TEWL on both the extensor and flexor sides of the forearm and back. We conclude that stratum corneum hydration, flexibility and thickness measured by the corneometer, and TEWL on the arm may be a useful indicator of the severity of ichthyosis phenotype.

DNA-based prenatal exclusion of bullous congenital ichthyosiform erythroderma at the early stage, 10 to 11 weeks' of pregnancy, in two consequent siblings

The proband was a Japanese woman with bullous congenital ichthyosiform erythroderma harboring a keratin 10 gene mutation M150T. DNA-based prenatal exclusion of bullous congenital ichthyosiform erythroderma was successfully performed in her two consequent pregnancies using chorionic villus samples at 10 to 11 weeks' gestation, several weeks earlier than the previously reported cases.