Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content +++ CUTANEOUS DISORDERS OF CORNIFICATION +++ Ichthyoses ++ Group of disorders characterized by generalized scaling of the skin Pathogenesis: increased cohesiveness of cells of the stratum corneum, abnormal keratinization, and abnormal proliferation +++ ICHTHYOSIS VULGARIS ++ Epidemiology: most common disorder of cornification; AD (Fig. 8-1) Pathogenesis Loss of function mutation in filaggrin (FLG) gene Increased adherence of the stratum corneum and scale formation is thought to result from a lack of water-retaining amino acids that derive from filaggrin metabolism Clinical features Not present at birth; onset during infancy/childhood Fine white, flaky scales develop on the extremities, especially the extensor surfaces with sparing of the groin and flexural areas due to increased humidity Improves with advancing age Associated with keratosis pilaris and atopic triad of asthma, hay fever, and eczema Pathology Thirty to fifty percent of affected individuals lack a granular layer on light microscopy and profilaggrin-containing keratohyalin granules by EM Treatment Emollients and humectants Keratolytics—be careful with salicylic acid to avoid salicylism Topical retinoids—can be irritating ++ FIGURE 8-1 Ichthyosis vulgaris. (Reprinted with permission from Freedberg IM et al: Fitzpatrick's Dermatology in General Medicine, 6th Ed. New York: McGraw-Hill; 2003, p. 487.) Graphic Jump LocationView Full Size||Download Slide (.ppt) +++ LAMELLAR ICHTHYOSIS ++ Epidemiology: AR (Fig. 8-2) Pathogenesis In the majority of patients, it is caused by transglutaminase-1 deficiency due to deleterious mutations in the TGM1 gene Has also been mapped to the ATP-binding cassette transporter gene (ABCA12) and the cytochrome P450 family 4, subfamily F, polypeptide 22 gene (CYP4F22) Clinical features Apparent at birth and persists throughout life Collodion baby Characterized by large, dark-brown, and plate-like scales that form a mosaic pattern with minimal to no erythroderma Ectropion, eclabium, and significant hypoplasia of nasal and auricular cartilage due to tautness of facial skin Variable palmoplantar keratoderma (PPK), may have alopecia and nail dystrophy Treatment Oral retinoids may be necessary from early childhood if severe Keratolytics limited secondary to irritation and systemic absorption Topical vitamin D3 derivatives, tazarotene, and formulations containing lactic acid and propylene glycol in a lipophilic cream base Palliation for heat intolerance Ophthalmologic evaluation ++ FIGURE 8-2 Lamellar ichthyosis. (Reprinted from Russell LJ et al. Linkage of autosomal recessive lamellar ichthyosis to chromosome 14q. Am J Hum Genet 1994;55:1146.) Graphic Jump LocationView Full Size||Download Slide (.ppt) +++ NON-BULLOUS CONGENITAL ICHTHYOSIFORM ERYTHRODERMA: ++ Epidemiology: AR Pathogenesis Mapped to 6 different genes: transglutaminase 1, ALOXE3, ALOX12B, ABCA12, CYP4F22, and NIPAL4. 12-LOX and eLOX sequentially function to generate epoxy alcohol metabolites, which are necessary for formation of the epidermal lipid barrier Clinical features Presents at birth with a collodion membrane Persists throughout life Characterized by intense erythroderma, white small powdery scale, ... Your Access profile is currently affiliated with [InstitutionA] and is in the process of switching affiliations to [InstitutionB]. Please select how you would like to proceed. Keep the current affiliation with [InstitutionA] and continue with the Access profile sign in process Switch affiliation to [InstitutionB] and continue with the Access profile sign in process Get Free Access Through Your Institution Learn how to see if your library subscribes to McGraw Hill Medical products. Subscribe: Institutional or Individual Sign In Error: Incorrect UserName or Password Username Error: Please enter User Name Password Error: Please enter Password Sign in Forgot Password? Forgot Username? Sign in via OpenAthens Sign in via Shibboleth You already have access! Please proceed to your institution's subscription. Create a free profile for additional features.