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Prenatal detection of trisomy for the entire long arm of chromosome 7
  1. B V NDAH*,
  2. JEFFREY A STEAD*,
  3. LEO R BRANCAZIO,
  4. MARYBETH HUMMEL,
  5. SHARON L WENGER*
  1. * Department of Pathology, West Virginia University, PO Box 9203, Morgantown, WV 26506-9203, USA
  2. Department of Obstetrics/Gynecology, West Virginia University, Morgantown, WV, USA
  3. Department of Pediatrics, West Virginia University, Morgantown, WV, USA
  1. Dr Wenger, swenger{at}hsc.wvu.edu

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Editor—Duplication of the long arm of chromosome 7 is extremely rare; most of the reported cases are partial trisomies. The first and only previous case of complete 7q duplication was reported in 1978 by Wahrman et al,1 who described a proband at 3 years of age with a phenotype including a large face with sloping forehead, downward slanting palpebral fissures, bilateral epicanthic folds, low set, malformed ears, short neck, and genitourinary and renal anomalies. Here we report a case of duplication of the whole of 7q with phenotypic characteristics similar to most reported cases of partial trisomy 7q, which include frontal bossing, low set, malformed ears, micrognathia, hypertelorism, and skeletal abnormalities.2 3 The extent of the duplication and verification of breakpoints were determined using FISH probes.

The patient was delivered by caesarian section at 34 weeks' gestation to a G1, P0, 15 year old female. She was first seen at 33 weeks' gestation when a sonogram showed multiple congenital anomalies including severe hydrocephalus, a two vessel umbilical cord, bowed femur, clubbed feet, and dilated kidneys.

At birth, the infant was cyanotic with Apgar scores of 3 and 4 at one and five minutes, respectively. She weighed 3000 g and was 41 cm long. Head circumference was 44 cm (average at 34 weeks' gestation is 31.5 cm). Multiple congenital anomalies were noted in addition to those seen on sonogram and included contractures of both hands and feet, missing digits from the left hand, contorted right hand, bilateral hip dislocation, low set, malformed ears, micrognathia, small mouth, high arched palate, hypertelorism, wide, beak-like bridge of the nose, increased intermammary distance, and pulmonary hypoplasia (fig 1). Mild to moderate tricuspid regurgitation was present. The infant was placed on a ventilator with 100% oxygen, but saturation did not improve. The infant died six hours after birth from respiratory failure.

Figure 1

The patient showing the physical features including hydrocephalus, low set ears, micrognathia, deformed hands and feet, hypertelorism, and small mouth.

At necropsy, additional congenital anomalies were noted, including a dilated, tortuous right ureter with kinking (fig 2). The lungs were markedly hypoplastic with dilated airways and apical blebs. The hydrocephalic brain contained about 500 ml of CSF in markedly dilated ventricles. The mesencephalic aqueduct was markedly stenotic.

Figure 2

Dilated, tortuous right ureter with kinking noted at necropsy.

Cytogenetic studies on percutaneous umbilical blood sampling (PUBS) obtained at 33 weeks' gestation and cultured fibroblasts obtained from the umbilical cord at birth showed a duplication of the entire long arm of chromosome 7. This was confirmed by a FISH probe for the elastin gene at 7q11.2 (Oncor). Three copies of the FISH probes for the elastin gene and markers at 7q36 were present in each metaphase analysed, indicating that the patient was trisomic for chromosome 7q. Dual labelled centromere probes for 7 (Oncor) and 15 (Vysis) identified two centromeres each, with the 15 centromere on the derivative chromosome, confirming 7q and 15p breakpoints. The patient's karyotype was 46,XX,der(15)t(7;15)(q11.2;p11.2) (fig 3). The mother's karyotype was normal, 46,XX; however, no sample was available from the father for analysis. A fibroblast cell line established from umbilical cord on the patient is available through Coriell Cell Repositories (Camden, NJ).

Figure 3

Cytogenetics. (A) Partial karyotype of the patient chromosomes 7 and 15, with the duplicated 7q translocated onto the short arm of chromosome 15 (on far right), (B) FISH confirmation of 7q duplication with three sets of signals for elastin and marker probes, and (C) FISH centromeric probes for 15 (long arrow) and 7 (short arrow). The der(15) is on the far left (long arrow).

Of all previously reported cases of trisomy 7q, there has been only one reported case involving duplication of the entire long arm of chromosome 7; we report the second case. Trisomy 7q produces abnormalities affecting virtually every system in the body including the central nervous system, the face, the musculoskeletal system, the heart, andthe genitourinary system, but the combination of specific malformations may vary among patients. Our case showed a number of features similar to the previously reported case of duplication of the whole of 7q by Wahrman et al,1 including frontal bossing, hypertelorism, low set, malformed ears, short neck, downward slanting palpebral fissures, and skeletal and kidney abnormalities. The features in our case not reported by Wahrman et al 1 include hydrocephalus, bilateral clubbing of the hands and feet, micrognathia, increased intermammary distance, and pulmonary hypoplasia.

The features in our case were also similar to those described in partial trisomies of 7q. The majority of reports of partial trisomy 7 result from a parental balanced translocation (reciprocal or insertion) or inversion 7. Clinical findings for duplications for 7q22q31, 7q31qter, and 7q32qter have been well accepted as having characteristic abnormalities.2 3 Because trisomies of other regions usually involve deletion of another chromosome region owing to missegregation of a balanced translocation or crossing over of an inverted 7, review of cases included those that only contained duplicated 7q material (table 1). Kidney abnormalities and lung hypoplasia have been reported in trisomy 7 and mosaic trisomy 7 cases.

Table 1

Clinical characteristics of duplication 7q and trisomy 7

Acknowledgments

We wish to thank Mrs Cindy Cutenese for her technical expertise.

References

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