A 23-year-old healthy African woman, mother of a healthy child, born by C-section for obstructed labor, presented at 12 weeks and 5 days' gestation of the second spontaneous pregnancy for the first trimester echography. The exam revealed an anechoic structure appearing like a possible right ureteral dilatation (Figure 1A). Both renal arteries seemed to be present with the Doppler evaluation (Figure 1B). First trimester scan exam including nuchal translucency was otherwise normal and combined test for Down syndrome has been evaluated at 1/30,000.
At 18 weeks' gestation, we had a strong suspicion of great arteries' malposition because of an abnormal three-vessel view. Regarding this suspicion, an amniocentesis was performed and revealed a male fetus with 22q11 deletion. The follow-up was made in a university center, and several echographic exams were performed. The first one at 19 week's gestation concluded to an anomalous pulmonary venous return and transposition of great vessels. The left renal agenesis was discovered at 25 weeks' gestation, and the ultrasound at 29 weeks' gestation showed a conotruncal cardiopathy with malposition of great arteries, interventricular communication, left renal agenesis, and penile hypoplasia. The transposition of great vessels described above was nullified.
The patient presented for premature rupture of membrane at 32 weekends and 4 days' gestation and delivered 2 weeks later a male fetus of 1578 g with the following features at necropsy: facial anomalies with hypotelorism, wide nasal bridge, low set right ear and microcephaly, and limb manifestations with postaxial bilateral hexadactyly without bone component (Figure 2). About urogenital anomalies, left renal agenesis and perineoscrotal hypospadias with penile hypoplasia (Figure 3) with descended testes were found. Concerning the cardiovascular and respiratory system, the exam revealed pneumothorax with subglottic perforation and tracheal stenosis, parathyroid aplasia, heart defect with "s shape" of ascending aorta without transposition (Figure 4A), and two punctate interventricular communications, one muscular and the other one, sub-arterial (Figure 4B). The baby probably died secondary to a tracheal stenosis, which limited the intubation.
First described in 1968, deletions in the chromosomal region 22q11 result from an anomaly of the third and fourth pharyngeal pouches during embryonic life. Also known as DiGeorge syndrome, velocardiofacial syndrome, and CATCH22 acronym (cardiac defects, abnormal faces, thymus hypoplasia, clef palate, and hypocalcemia) that outlines the main clinical features, this deletion presents an expansive phenotype with more than 180 clinical features described that involve every organ and system. It occurs in 1/4000 live births and constitutes the most frequent interstitial chromosomal aberration.
Researchers are working to identify all of the genes that contribute to the features of 22q11.2 deletion syndrome. They have determined that the loss of a particular gene on chromosome 22, TBX1, is probably responsible for many of the syndrome's characteristic signs (such as heart defects, a cleft palate, distinctive facial features, hearing loss, and low calcium levels). The loss of additional genes in the deleted region likely contributes to the varied features of 22q11.2 deletion syndrome.