P02.71: Prenatal diagnosis of Meckel‐Gruber syndrome

Abstract

Meckel-Gruber syndrome is a rare and lethal autosomal recessive disorder characterized by occipital encephalocele, polydactyly and bilateral dysplastic cystic kidneys. Antenatal ultrasound examination can establish the correct diagnosis by identifying at least two of the major features described. We report a case in which the diagnosis of Meckel-Gruber Syndrome was possible by transvaginal sonography in the first trimester. A 30-year-old, prima-gravida patient presented for sonography at 13 weeks to have the nuchal translucency screening test. The transabdominal scan revealed occipital encephalocele of the fetus. The CRL was 80.3 mm and the NT measurement was 2.1 mm. There was no oligohydramnios, but the fetal urinary bladder was not visualised. The transvaginal sonogram demonstrated an encephalocele involving the posterior fossa with a large posterior fossa cyst protruding from the occiput. The kidneys were echogenic, suggesting cystic dysplasia, and there was evidence of polydactyly of the hands. Based on these findings, the diagnosis of Meckel-Gruber Syndrome was made. The patient elected to terminate the pregnancy, and the diagnosis was confirmed after delivery. The incidence of Meckel-Gruber Syndrome worldwide varies from 1 in 13,250 to 1 in 140,000 live births. It is an autosomal recessive disorder with a recurrence risk of twenty-five percent. The locus for Meckel syndrome is on chromosome 17, long arm, region 2, and bands 1–4. The reported incidence of renal disorder in this syndrome varies from 95% to 100%. Occipital cephalocele is present in 60% to 80% of fetuses. Post-axial polydactyly is present in 55% to 75%. Other limb anomalies such a bowing and shortening may also be present. A karyotype study should be obtained when Meckel syndrome is suspected, to exclude chromosomal disorders. If the diagnosis is made, termination can be offered. Parents should be counseled of the likely recurrence of Meckel-Gruber syndrome.