EP03.07: Prenatal diagnosis of 22q11.2 microdeletion: minor cardiac finding detected in mid-trimester scan associated with severe bilateral perisylvian polymicrogyria in late gestation

A microdeletion in chromosomal region 22q11.2 results in DiGeorge syndrome (OMIM 188400) and velocardiofacial syndrome (OMIM 192430). The most frequent findings in 22q11.2 microdeletion are facial dysmorphism, velopharyngeal insufficiency, conotruncal cardiac abnormalities (usually associated with thymic hypoplasia), and speech delay. Polymicrogyria (PMG) is a rare feature of the microdeletion presenting with developmental delay, microcephaly, and epilepsy. We report the case of a male fetus, whose 23 weeks anatomical scan depicted two right pulmonary arterial vessels (instead of one) observed in longitudinal plane through the aortic arch. In view of the otherwise normal fetal echocardiography, this finding was interpreted as proximal bifurcation of right pulmonary artery. At 30 weeks sonographic scan, malformation of cortical development was suspected. The scan revealed bilateral dysmorphic and shallow Sylvian fissures with irregular cortical surface, surrounded by enlarged subarachnoid spaces. MRI performed at 32 weeks depicted frontal loss of brain volume with irregular dysmorphic cortex, mainly in the perisylvian regions, consistent with severe polymicrogyria. In view of poor prognosis, the parent asked to terminate the pregnancy. Fetal autopsy revealed perisylvian polymicrogyria, hypoplastic thymus, and unilateral anorchia. Microdeletion in 22q11.2 region was detected on fetal CMA. Revision of the 2nd trimester scan demonstrated normal brain anatomy, however the thymus was small for gestational week. Conclusions: Minor finding in great vessels associated with hypoplastic thymus can be associated with severe PMG in late gestation as a result of 22q11.2 microdeletion.