Balkan Journal of Medical Genetics

A SYSTEMATIC CLINICAL REVIEW OF PRENATALLY DIAGNOSED TETRASOMY 9p
Vinkšel M, Volk M, Peterlin B, Lovrecic L*
*Corresponding Author: Luca Lovrecic, M.D., Ph.D., Assistant Professor, Clinical Institute of Medical Genetics, University Medical Centre Ljubljana, Zaloska cesta 002, SI-1000 Ljubljana, Slovenia. Tel: +386-1-522-6057. Fax: +386-1-540-1137. E-mail: luca.lovrecic@kclj.si
page: 11

RESULTS

words. After applying selected criteria, 21 cases of prenatally detected tetrasomy 9p in 18 different publications remained for detailed analysis. We added our prenatal case, resulting in 22 cases altogether. Of these, 15 cases were related to full tetrasomy 9p and seven cases were a mosaic form of tetrasomy 9p. A further four publications were identified describing trisomy 9p detected prenatally and were suitable for comparison of tetrasomy 9p and trisomy 9p phenotype [53-56]. Altogether, most of the reported cases of tetrasomy 9p were associated with severe congenital abnormalities. The most common prenatally detected features of tetrasomy 9p were central nervous system (CNS) abnormalities (13/22) (our case [3,5,7,15,32,33,37-40,45,47]), limb/ skeletal malformations (11/22) (our case [1,5,7,32,38- 40,45,47,51)], intrauterine growth retardation (IUGR) (10/22) [1,3-5,7,33, 38,39,46], cleft lip and/or palate (10/22) (our case [1,5, 32,38, 39,45-47)], and facial dysmorphism (8/22) (our case [5,7,39,40,45,46)]. All the details and less common anomalies are presented in Tables 1 and 2. The type of fetal anomalies were further analyzed related to fetal gestational age at their discovery (details are presented in Table 3). A total of six cases of tetrasomy 9p were detected in the first trimester based on abnormal ultrasound assessment. The most common phenotypic feature was increased NT (4/6) (our case [5,39,45]), usually accompanied by at least one more anomaly (cleft lip and/or palate, skeletal abnormalities, IUGR, and facial dysmorphism). A single case presented with isolated increased NT only (our case). In the latter, chorionic villus sampling was performed after genetic counseling. Microarray analysis detected a tetrasomy 9p with 38.6 Mb four copies of the region 9p24.3p13.2 (arr[GRCh37]9p24. 3p13.1(204193_38815475)×4). The GTG banding and FISH analysis of 35 metaphase spreads revealed a pseudoisodicentric chromosome 9 consisting of the two p arms, two centromere regions and two q arm segments with a breakpoint at 9q13 (47,+psu idic(9)(q13) [Figure 1(A-C)]. In 10 cases of tetrasomy 9p, the abnormal ultrasound findings were reported in the second trimester. The most common fetal anomalies were CNS abnormalities (8/10) [5,7,15,32,33,37,39,45], genitourinary tract anomalies (6/10) [5,32,37,39,45], skeletal/limb abnormalities (5/10) (our case) and facial dysmorphism (5/10) (our case [5,7,39, 45]). Additional anomalies were discovered in less than five cases. An additional three cases were identified only after a third trimester ultrasound scan, presenting with IUGR and additional CNS and skeletal/limb abnormalities. For the remaining cases it was not possible to determine the precise time of the prenatal diagnosis (PND). When comparing the genotype-phenotype correlation in the group of mosaic (seven cases) vs. full tetrasomy 9p (15 cases), less severe phenotypes were reported in mosaic cases, still including the same plethora of phenotypic features (Table 3). The prenatally detected cases of tetrasomy 9p with lower levels of mosaicism presented with the involvement of only one organ system or without any major structural anomalies. One case presented with IUGR, the second with cardiac anomaly and the third with fetal ascites and hydrops fetalis. All mosaic cases were detected after amniocentesis [1,4,5,33,34,38,52], with the lowest level of mosaicism being 15.8% [52] and the highest level of 96.7% [1]. Lastly, we were interested in gene dosage effect, therefore, prenatal cases of tetrasomy 9p and trisomy 9p were compared [53-56]. The clinical phenotype in trisomy 9p was similar to that described in tetrasomy 9p only milder. Pregnancy outcome following PND of tetrasomy 9p were termination of pregnancy in 14/22 cases (our case [4,5,7,15,32,34,37,39,40,46,52]), neonatal death (3/22) [3,38,45], intrauterine death (1/22) [1] and a child who survived to at least 4 years of age [33] (Table 4). For the remaining three cases this information was not provided. Only the mosaic forms of tetrasomy 9p survive past the neonatal period, whereas full tetrasomy 9p has a fatal outcome.

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