Fetus with two identical reciprocal translocations: description of a rare complication of consanguinity.
We report on a 24-week fetus with multiple organ anomalies secondary to biparental inheritance of an apparently balanced t(17;20) reciprocal translocation. The pregnancy was terminated following the discovery by ultrasound of an abnormal heart and micrognathia. At autopsy, the following anomalies were found: Pierre-Robin sequence, hypoplasia of the right ventricle with muscular hypertrophy, and endocardial fibroelastosis, hypoplastic lungs, dysplastic left kidney, bilateral pelvicalyceal dilatation, central nervous system periventricular heterotopias and right sided club foot. Given the endocardial fibroelastosis and cleft palate, Eastman-Bixler syndrome (Facio-cardio-renal) is a possible diagnosis. The parents were first cousins and each had an identical t(17;20)(q21.1;p11.21) translocation. The fetal karyotype was 46,XX,t(17;20)(q21.1;p11.21)mat,t(17;20)(q21.1;p11.21)pat. While there are a few reports of consanguineous families where both the mother and father had the same reciprocal translocation and offspring with unbalanced karyotypes, we were unable to find any reports of a fetus/child with double identical reciprocal translocations. We propose that although the fetus had an apparently balanced karyotype, inheriting only the translocated chromosomes led to the unmasking of a recessive syndrome. It seems most likely that a gene (or genes) was disrupted by the breaks but the parents might also be heterozygous carriers of a recessive gene mutation since the fetus must be homozygous by descent for many loci on both chromosomes 17 and 20 (as well as on other chromosomal segments). It was not possible to totally exclude segmental uniparental disomy as a cause of the anomalies as no recombinations were detected for chromosome 17. However, there is no evidence to suggest that chromosome 17 is imprinted and UPD 20 was excluded thus making an imprinting error unlikely.
Martinet
Danielle
D
Service of Medical Genetics, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
Vial
Yvan
Y
Thonney
Francine
F
Beckmann
Jacques S
JS
Meagher-Villemure
Kathleen
K
Unger
Sheila
S
D000015:Abnormalities, Multiple / Q000235:genetics / Q000473:pathology; D000025:Abortion, Eugenic; D002871:Chromosome Banding; D002886:Chromosomes, Human, Pair 17 / Q000235:genetics*; D002890:Chromosomes, Human, Pair 20 / Q000235:genetics*; D003241:Consanguinity; D005145:Face / Q000002:abnormalities; D005260:Female; D005313:Fetal Death; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D008297:Male; D008844:Micrognathism / Q000473:pathology; D010375:Pedigree; D014178:Translocation, Genetic