My grandchild has been diagnosed with ichthyosis and pityriasis rubra pilaris. These are very difficult conditions for a child to deal with emotionally and physically. Has there been any effort to treat them through gene therapy?—LINDA BANNICK, RN, SNP, Dallas

Congenital ichthyosis is a group of diseases considered to be disorders of cornification. These conditions have abnormalities in the manufacture or desquamation of keratinocytes. The genetic defect has been identified for many of these diseases: (1) a post-translation defect in profilaggrin expression in autosomal dominant ichthyosis vulgaris; (2) a deficiency of steroid (cholesterol) sulfatase in x-linked recessive ichthyosis; (3) a mutation in keratins 1 and/or 10 in autosomal dominant epidermolytic hyperkeratosis (bullous congenital ichthyosiform erythroderma); and (4) various mutations in the transglutaminase-1 gene in autosomal recessive congenital ichthyosis (a term used to include both lamellar ichthyosis and nonbullous congential ichthyosiform erythroderma [often referred to as congenital ichthyosiform erythroderma]) (Am J Clin Dermatol. 2004;5:17-29). Pityriasis rubra pilaris is a papulosquamous dermatosis that is uncommon in children; however, in juveniles, it can occur in either a generalized or localized presentation. The genetic defect in pityriasis rubra pilaris remains to be identified ( J Am Acad Dermatol. 2008;59:943-948 and 2002;47:386-389). Since the genetic defects for many of the ichthyosis diseases have been identified, there is potential for the development of gene therapy in these conditions (Acta Derm Venereol. 2008;88:4-14, J Gene Med. 2001;3:21-31, and Histochem Cell Biol. 2001;115:73-82).—Philip R. Cohen, MD (137-13)