DNA-based Prenatal Diagnosis of Epidermolytic Palmoplantar Keratoderma in Two Pregnancies at Risk in One large Pedigree

BACKGROUND: Epidermolytic palmoplantar keratoderma (EPPK) is an autosomal dominant disease of cornification which presents as severe thickening of the palms and soles with prominent epidermolytic hyperkeratosis pathologically. Recent studies have shown that EPPK is caused by mutations in the keratin 9 (K9) gene which is expressed essentially only in the palms and soles. Previously, We have reported that patients in one large pedigree of EPPK have an R162W substitution in the K9 protein. In this pedigree, two women whose husbands are both EPPK patients had become pregnant. OBJECTIVE: Since both women were concerned about this genetic disorder, we have performed prenatal diagnosis by biopsy analysis of chorionic villi tissue. METHODS: Chorionic villi biopsies were performed at 12 weeks gestation. Since the skin lesions are strictly confined to the palms and soles of the babies, the prenatal diagnosis of EPPK by ultrastructural analysis of fetal skin biopsy or amniotic fluid cells is highly problematic. Polymerase chain reaction amplification of specific allele (PASA) assay and direct DNA sequencing analyses were performed whether the fetuses carried mutant allele of K9 gene. RESULTS: PASA assay and direct DNA sequencing analyses showed that one fetus was normal, but the other fetus carried the abnormal allele. Subsequently, the mother of the unaffected fetus delivered a normal child, but the mother of the affected fetus terminated the pregnancy. CONCLUSION: We describe the analysis of the K9 mutation in the two fetuses at risk for EPPK. We believe that this is the first report of prenatal diagnosis for EPPK. But, we have to think about the ethical problems before we decide to perform the prenatal diagnosis of any kind of skin diseases.

DNA - based Prenatal Diagnosis of Epidermolytic Palmoplantar Keratoderma / 대한산부인과학회잡지

OBJECTIVE: The purpose of this investigation was to establish the prenatal diagnosis for identifying the risk for epidermolytic palmoplantar keratoderma(EPPK) of a fetus by sequence analysis of fetal genomic DNA from chorionic villi. METHODS: Chorionic villus sampling under transvaginal sonography at 12 weeks of gestation from a woman at risk for a child in a EPPK-affected family was perfomed. Polymerase chain reaction amplification of specific allele (PASA) assay was carried out for the detection of mutation(R162W in keratin 9 [K9] gene) previously identified in this family. Direct DNA sequencing analysis of K9 gene was accomplished to confirm the mutation. RESULTS: We had found the point mutation, R162W of K9 gene, in affected family members and confirmed by PASA assay. Affected family members were shown to have PCR products reactive with both the mutant and wildtype specific primers. Because we could not find any expected products after PASA assay with the primers la(+)/KSmt(-) of the fetal DNA, we predicted that the fetus did not inherited the mutant allele and that the fetus could be unaffected. After PASA assay, we analyzed DNA sequences of two family members to confirm the mutation. A C-to-T substitution at bp 545 was detected in the father, instead the fetus did not have any mutant band at that base pair. CONCLUSION: The PASA assay and direct DNA sequencing analysis of K9 gene through chorionic villi sampling and extraction of genomic DNA had validity to early prenatal diagnosis whether fetus was affected in EPPK or not.