Disorders of keratinization: diagnosis and management.

Disorders of cornification are a group of diseases that share abnormalities in the manufacture or desquamation of corneocytes. This paper reviews the major and a few of the rarer ones with a concentration on their therapy. Ichthyosis vulgaris is probably a post-translational defect in pro-filaggrin expression. It shows fine white flaky scales of the extensor surfaces, trunk, flank, lower legs but spares the folds and wet areas. Treatment is with aggressive moisturization. Hydrocortisone creams may be needed to control itch. Recessive X-linked ichthyosis is due to a deficiency of cholesterol sulfatase. Boys with this condition show small dark scales around the ears, sides of the neck, extensor surfaces of the arms and legs, and the peri-umbilical region. It spares the folds and face. Treatment is with moisturizers, topical retinoid creams or with topical cholesterol-based creams. Checking for signs of contiguous gene disorders (Kallman or Conradi-Hunermann syndromes) is necessary. Bullous congenital ichthyosiform erythroderma is caused by mutations in keratins 1 and/or 10. These patients are born as bright red babies with large blisters and erosions. Slowly, a porcupine quill-like waxy scaling develops. Blistering continues throughout life. Secondary infections of the skin cause pain, debility, and a very foul odor. Treatment is difficult. Topical moisturizers, descalers and retinoid creams help a little. Oral retinoids help a lot but can cause increased blistering. Controlling the odor is an ongoing issue using antibacterial washes, absorbing powders, and masking fragrances. Autosomal recessive ichthyosis is a term for both lamellar ichthyosis and congenital ishthysosiform erythroderma. They are caused by various mutations in transglutaminase-1 gene. In both instances patients are born as 'collodion babies'. Lamella ichthyosis has the very recognizable plate-like scale over the entire body. Children with congenital ishthysosiform erythroderma are red all over with a finer scale in some places and plate-like scales in others. Treatment is with topical moisturizers, retinoid creams, descalers, and in some cases oral retinoids. Palmar plantar keratodermas occur in conjunction with some ichthyoses, but also by themselves. Some are diffuse and others have discrete, corn-like hardenings. Treatment with topical acids, propylene glycol and retinoid creams help to some extent.Throughout the article pearls from my practice are included to assist the clinician in the day-to-day handling of these patients. A short section on genetic counseling concludes this article.