Molecular mechanisms of genetic disorders of keratinization.

An attempt is made to organize our current knowledge about genetically determined disorders of keratinized tissue, which primarily affect the epidermal structural proteins. Type I defects are those involving a change in a single amino acid and are analogous to sickle cell anemia. Type II defects are associated with abnormal retention of a normal structural protein intermediate. Type III defects are related to alterations in the normal post-translational cross-linking seen in keratinized tissues. Type IV defects are associated with altered proportions of fibrous proteins and are analogous to thalassemia. In type V defects, primary genetic disorders of other tissues profoundly affect keratinization in a secondary fashion. Examples from genetic disorders of the hair and epidermis are used to build this conceptual scheme.