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During the last decade, our understanding of the molecular bases for genetic disorders of the skin has expanded tremendously. Identifying the gene mutations that lead to phenotypic manifestations facilitates prenatal diagnosis using molecular techniques. For some disorders, this information has translated into early trials of gene therapy or the development of new pharmacologic therapy based on manipulation of gene product levels. Several support groups that provide education for patients and physicians are available and are listed for each subgroup of genetic disorders of skin. The National Organization for Rare Disorders (NORD) at can also help families for whom there is no specific support group. More information about specific genetic disorders can be found at and about the availability of genetic testing at

Named for the Greek term meaning “fishlike scales,” this heterogeneous group of disorders is characterized by the predominant clinical feature of visible accumulation of scale. FIRST (Foundation for Ichthyosis and Related Skin Types) is a national support group for patients with the ichthyoses and other disorders with thickening of epidermis ( During the past decade, the underlying molecular basis for many of the ichthyotic disorders has been discovered, and many can be diagnosed prenatally through molecular analysis of genomic DNA obtained by chorionic villus sampling or amniocentesis. If possible, specific diagnosis should be made as early as possible to aid in prognostication and genetic counseling. In general, therapy for these disorders is similar and is based on disease severity and tolerance rather than the specific type. During the neonatal and early infantile period, however, therapy should be limited to the frequent application of bland emollients, since use of topical medications with keratolytic agents during the first 6 months of life is usually unnecessary and risks significant absorption of potentially toxic substances (eg, absorption of lactic acid, salicylic acid).

Scaling in the genetic forms is usually either present at birth or has its onset within the first few years of life. Rarely, nongenetic causes lead to ichthyosis in pediatric patients. Causes of acquired ichthyosis include hypothyroidism, chronic renal insufficiency, malignancy (particularly lymphoma), malabsorption syndromes, essential fatty acid deficiency, sarcoidosis, and certain drugs (particularly hypocholesterolemic agents).

Ichthyosis vulgaris is the most common form of the ichthyoses.1,2 It is now known to result from mutations in the gene encoding filaggrin, a gene also recently implicated in atopic dermatitis. Approximately 1 in 20 Northern European individuals carry a mutation on 1 allele and have a mild form; homozygotes have a much more severe form. Thus, the disorder is not autosomal dominant, as was once thought, but is semidominant. Regardless of severity, the onset of scaling in ichthyosis vulgaris tends to be after 3 months of age and may become more prominent later during childhood or at puberty. Fine, white scales, often without much erythema, predominate on the exterior surfaces of the extremities, especially the legs (Fig. 360-1). There is ...

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