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September 2001

Expanding Our Concepts of Mosaic Disorders of Skin

Arch Dermatol. 2001;137(9):1236-1238. doi:10.1001/archderm.137.9.1236

DURING THE past decade, our understanding of the role of keratins in ectodermal structures has led to the discovery of the molecular bases of several genetic disorders of skin (for reviews, see Irvine and McLean1 and Corden and McLean2). Keratin gene mutations in patients with epidermolysis bullosa simplex were first described in 1991, after generation of a transgenic mouse model with deletion of a critical region of keratin 14 (K14) that resembled the human phenotype of the Dowling-Meara subtype. The known localization of specific keratin gene expression in epidermis and other ectodermal sites then led to the discovery of K1 and K10 keratin gene mutations in patients with epidermolytic hyperkeratosis (EH, ichthyosis bullosa of Brocq); K2e mutations in ichthyosis bullosa of Siemens; K9 mutations in the epidermolytic (Vorner) form of palmoplantar keratoderma; K6a, K6b, K16, and K17 mutations in pachyonychia congenita; K4 and K13 mutations in white sponge nevus; and mutations in hair keratins hHb1 and hHb6 in patients with monilethrix. Each type I keratin has an obligate type II keratin partner with which it pairs in a tissue-specific and differentiation-specific manner, eg, K5 and K14, K1 and K10, K6a and K16, K6b and K17, and K4 and K13 (for review, see Irvine and McLean1); thus, mutations in the genes of either keratin partner could theoretically cause a similar phenotype.

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