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Prenatal diagnosis of Desbuquois dysplasia Type 1: Utilization of high‐density SNP array to map homozygosity and identify the gene
Author(s) -
Forster Katherine R.,
Hooper Jody E.,
Blakemore Karin J.,
Baschat Ahmet A.,
HooverFong Julie
Publication year - 2019
Publication title -
american journal of medical genetics part a
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.064
H-Index - 112
eISSN - 1552-4833
pISSN - 1552-4825
DOI - 10.1002/ajmg.a.61372
Subject(s) - disease gene identification , candidate gene , genetics , snp array , prenatal diagnosis , medicine , single nucleotide polymorphism , dysplasia , genetic testing , exome sequencing , pregnancy , fetus , biology , mutation , gene , genotype
Desbuquois dysplasia (DBQD1 [MIM 251450]) is an autosomal recessive chondrodysplasia with micromelia, severe joint laxity and dislocations, and a characteristic radiographic “monkey wrench” appearance at the proximal femur. Type 1 Desbuquois dysplasia is caused by mutations in CANT1 and is distinct from Type 2, caused by mutations in XYLT1 , in that the former has unique hand anomalies including accessory phalangeal ossification centers, advanced carpal bone maturation, and/or axial phalangeal deviation. Severe prenatal presentations have been rarely reported. We report a Pakistani female in a consanguineous relationship with a diagnosis of Type 1 Desbuquois dysplasia in three consecutive pregnancies. Multiple similar severe fetal limb anomalies were detected by ultrasound in Pregnancy 1 and 2. Regions of homozygosity within the single nucleotide polymorphism (SNP)‐microarray from both terminated fetuses were compared, revealing CANT1 as a likely disease‐causing candidate gene. Insufficient fetal DNA precluded confirmatory testing, therefore parents were tested; both had a previously reported heterozygous CANT1 mutation (c.643G>T; Glu215Term). The patient presented with a third pregnancy revealing similarly abnormal limb position and probable polysyndactyly by ultrasound. Targeted testing of CANT1 revealed homozygous c.643G>T CANT1 mutations and this pregnancy was terminated. In clinical situations in which ample DNA is not available or more expensive testing (e.g., whole exome sequencing) with a longer turnaround time is not feasible, utilization of SNP‐microarray in consanguineous families at risk for rare autosomal recessive disorders may dramatically narrow the list of candidate genes.