Prenatal diagnosis ofde novo interstitial 16q deletion in a fetus associated with sonographic findings of prominent coronal sutures, a prominent frontal bone, and shortening of the long bones

Chromosomal deletions detected at amniocentesis

OBJECTIVE

The aim of this study is to present the incidence, prenatal and postnatal findings, and modes of ascertainment in chromosomal deletions detected at amniocentesis.

MATERIALS AND METHODS

We reviewed all the cases with chromosomal deletions, which were detected by amniocentesis in Mackay Memorial Hospital, Taipei, Taiwan, between January 1987 and December 2012. Data on the locations and types of deletion, reasons for performing amniocentesis, maternal age, gestational age at amniocentesis, fetal karyotypes, inheritance of deletions, and relative prenatal findings were collected.

RESULTS

Amniocentesis was performed in 33,305 cases within this period of time. Among these, 31 cases of chromosomal deletions were considered for the study. The mean gestational age at amniocentesis was 21.0 weeks (range from 15 weeks to 32 weeks) and the mean maternal age at amniocentesis was 32.1 years (range from 26 years to 37 years). Nineteen cases (61.3%) manifested fetal structural abnormalities on ultrasound, nine (29.0%) presented no ultrasound abnormalities, and three had an unknown status. The main modes of ascertainment included abnormal ultrasound findings in 10 cases (32.2%), advanced maternal age in 11 cases (35.5%), abnormal maternal serum screening results in six cases (19.6%), and other reasons in four cases (13.0%). Of the 27 cases with known inheritance, the deletion was inherited in two (6.6%) and de novo in 25 (92.6%). Males accounted for 11 (35.5%) and females for 20 (64.5%) cases. Chromosomal deletions are more often to occur in chromosomal 5(4 cases, 12.9%), chromosomal 18 (4 cases, 12.9%), chromosomal 4 (3 cases, 9.7%), chromosomal 7 (3 cases, 9.7%), chromosomal 10 (3 cases, 9.7%), chromosomal 11 (3 cases, 9.7%), and chromosomal 1 (2 cases, 6.5%). There were four cases of chromosomal mosaicism: two involved chromosome 5, one involved chromosome 10, and one involved chromosome 18. Twenty-three cases (74.2%) had terminal deletions and the other eight cases (26.7%) had interstitial-type deletions.

CONCLUSION

In summary, we have presented the results of prenatal diagnosis for chromosomal deletions using amniocentesis. Chromosomal deletions are more likely to occur in females and more often in chromosomal 5p and 18q. Prenatal diagnosis at amniocentesis is frequently associated with advanced maternal age, abnormal ultrasound findings, and abnormal maternal serum screening. The frequency of ascertainment in chromosome deletion seems to be directly correlated with advanced maternal age and abnormal ultrasound findings. In cases with terminal deletions, prenatal ultrasound plays a more important role for prenatal diagnosis.

Tetralogy of Fallot associated with pulmonary atresia and major aortopulmonary collateral arteries in a patient with interstitial deletion of 16q21-q22.1

A newborn male had an interstitial deletion of 16q21-q22.1 accompanying tetralogy of Fallot associated with pulmonary atresia and major aortopulmonary collateral arteries (MAPCA), dysmorphic craniofacial features, failure to thrive, and severe psychomotor developmental delay. When the deletion in this patient and other reported patients are compared, the 16q22 region appears to be the smallest region for 16q deletion syndrome. Since over 50% of patients with the deletion of 16q22 region have congenital heart disease, there may be a responsible gene in this region.