Disorders of Keratinization

This chapter describes a variety of skin disorders that have as their basis a disorder of keratinization. The term Mendelian disorders of cornification (MEDOC) have recently been used to classify these conditions. The genetics underlying the ichthyoses is complex; to date there are 36 forms of inherited ichthyosis, including conditions primarily affecting the skin, and rarer ‘syndromic’ associations involving other organs. The chapter reviews the more commonly encountered ichthyoses, including ichthyosis vulgaris, recessive X-linked ichthyosis, and autosomal recessive congenital ichthyoses. There are three major types of autosomal recessive congenital ichthyosis: lamellar ichthyosis, congenital ichthyosiform erythroderma and harlequin ichthyosis. The chapter also discusses other disorders of keratinization such as keratosis pilaris, keratosis follicularis and keratoderma of the palms and soles.