Prenatal diagnosis of a pair of twins with thanatophoric dysplasia type I and Down syndrome: a case report
Keywords:
Down syndrome, Prenatal diagnosis, Thanatophoric dysplasiaAbstract
We present a case of spontaneous dichorionic diamniotic twins, each affected by thanatophoric dysplasia type I and Down syndrome. Non-invasive prenatal screening revealed an increased level of chromosome 21 DNA. Ultrasound showed that twin A had short long bones and a bowed humerus, whereas twin B appeared phenotypically normal. Amniocentesis of twin A sent for quantitative fluorescent-polymerase chain reaction (QF-PCR), chromosome microarray, and sequence analysis of the fibroblast growth factor receptor 3 gene (FGFR3) identified a heterozygous variant in exon 7 of FGFR3, suggestive of autosomal dominant thanatophoric dysplasia type I (OMIM 187600). Amniocentesis of twin B sent for QF-PCR revealed trisomy 21, likely caused by meiotic nondisjunction, with normal chromosomes 13 and 18; karyotyping showed 47,XY,+21, suggestive of Down syndrome. At 22 weeks and 2 days of gestation, termination of pregnancy for both twins was performed.
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