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Increased nuchal translucency thickness in thrombocytopenia‐absent‐radius syndrome

2005; Wiley; Volume: 26; Issue: 5 Linguagem: Inglês

10.1002/uog.1998

1469-0705

Ingrid Witters, P. Claerhout, J. P. Fryns,

Urological Disorders and Treatments

Thrombocytopenia-absent-radius (TAR) syndrome is an autosomal recessive disorder characterized by bilateral radial aplasia with normal thumbs and thrombocytopenia (platelet count < 100 000/mm3). Various associated anomalies can occur with TAR syndrome: skeletal defects (femoral, ulnar, humeral hypoplasia); renal defects (horseshoe kidney); and cardiac defects (30% of affected children: ventricular septal defect; atrial septal defect; tetralogy of Fallot; coarctation of the aorta)1. We report on the second pregnancy of a nonconsanguineous couple whose first child was stillborn and had presented with bilateral absent radii and thrombocytopenia. Fetal ultrasound examination at 12 weeks' gestation (crown–rump length, 60 mm) revealed increased nuchal translucency (NT) (3.9 mm, > 99th centile) and bilateral absent radii (Figures 1 and 2). The nasal bone was present. Karyotyping following chorionic villus sampling revealed a normal male karyotype and absence of chromosome breakage. The parents were counseled about the poor prognosis and opted for termination of pregnancy. Pathological examination confirmed the ultrasound findings (Figure 3). Both thumbs were normal, as were the findings on cardiac examination. Ultrasound image showing increased nuchal translucency thickness at 12 weeks' gestation. Ultrasound image showing absent radius at 12 weeks' gestation. Postmortem photograph showing the fetus with bilateral absent radii and normal thumbs. The main differential diagnoses of bilateral absent radii include: Roberts-X syndrome (phocomelia often associated with facial clefting and chromosome instability; autosomal recessive); Fanconi anemia (aplastic anemia, abnormal thumbs and radial anomalies, chromosome instability; autosomal recessive) and Holt-Oram syndrome (bilateral asymmetric preaxial radial ray defects and cardiovascular anomalies; autosomal dominant). Roberts-X syndrome and Fanconi anemia were both reported to initially present with increased NT2. Unilateral absence of the radius can occur in trisomy 183. The prenatal diagnosis of TAR syndrome is usually made by the ultrasonographic detection of bilateral absent radii and by fetal blood sampling revealing thrombocytopenia3-11. Souter et al.12 reported a monochorionic twin pregnancy with increased NT at 12 weeks in both twins, absent humeri, radii and ulnae in one twin and bilateral absent radii in the other twin. The main differential diagnosis was Roberts-X syndrome or TAR syndrome. The bilateral absence of humeri in one twin makes the diagnosis of TAR syndrome in this report less likely12. In the present case the pregnancy was at risk for TAR syndrome, and both bilateral absent radii and increased NT thickness were noted at the 12-week scan. The pathophysiology for this increased NT remains unclear. However, increased nuchal skinfold thickness has been reported in individuals with TAR syndrome13. Fetal anemia, when attributable to genetic causes, can present with increased fetal NT2, and since some cases of TAR syndrome are associated with anemia as well as thrombocytopenia11 this could offer a possible explanation for the increased NT. This case adds to the long list of genetic syndromes associated with increased NT. I. Witters*, P. Claerhout , J. P. Fryns , * Department of Obstetrics Gynecology, University Hospital Gasthuisberg, Herestraat 49, 3000 Leuven, Belgium, Gynecologist, Stedelijk Ziekenhuis OCMW, Roeselare, Belgium, Center for Human Genetics, University of Leuven, Leuven, Belgium