Meckel Gruber syndrome antenatal diagnosis with postnatal confirmation

Clinical History

Twenty-three-year-old primigravida came for anomaly scan at 21 weeks of gestation, with history of consanguineous marriage. Past and family histories were noncontributory. She was not on any teratogenic drugs. Routine antenatal scan showed abnormal features. With the consent of parents, termination of the pregnancy was undertaken.

Imaging Findings

Meckel Gruber syndrome (MGS) was diagnosed on pre-natal ultrasonogram (Figs. 1, 2, 4, 6, 7) and findings were confirmed on autopsy (Figs. 3, 5, 8, 9).

The occipital bone of calvaria was deficient with outpouching of the neural contents suggestive of occipital meningoencephalocele (Figs. 1, 3-5).

The rest of the fetal biometry corresponded to gestational age (Fig. 6).

Sonogram revealed diffusely hyperechoic enlarged kidneys and oligohydroamnios (Figs. 7-9).

The mother underwent a normal vaginal delivery of a stillborn baby at 21 weeks of gestation.

Postnatally we confirmed the findings of cervico-occipital meningocele and webbed neck.

Further autopsy confirmed rest of the findings.

The first sonographic finding in most cases is oligohydramnios, due to renal dysfunction, and it develops early in the second trimester [1].

MGS is a lethal disorder. Most infants are stillborn or die hours or days after birth [2]. Parents should be counselled about the likely recurrence [3].

Discussion

Being a rare lethal congenital foetal anomaly; Meckel Gruber syndrome (MGS) reinforces the notion, “prevention is better than cure”. Although being rare, the likelihood of recurrence in subsequent pregnancies cannot be ignored. Ultrasonography aims to detect the syndromic changes at the earliest, and helps reduce the unfruitful burden on the health of the mother [1].
Renal cystic disease, occipital meningoencephalocele and post axial polydactyly are most consistent features. Two out of the three criteria mentioned above are a must to diagnose MGS. The disease affects all races with males and females being equally affected. The present patient is a non-gujarati Indian whose diagnosis was confirmed by neonatal autopsy.
MGS involves multiple organ systems of the body; known spectrum of central nervous system involvement has a wide range including holoprosencephaly, total craniorachischisis, absences of olfactory lobes and tract, cerebellar hypoplasia, Dandy Walker malformation, Arnold Chiari Malformation, schizencephaly, agenesis of corpus callosum and partial defect of corpus callosum [2].
When MGS is suspected, other associated congenital malformations to be keenly looked for include hepatic fibrosis, atrial septal defect, coarctation of aorta, ductal agenesis, portal fibrosis, cleft lip and cleft palate, hypo/hypertelorism, pulmonary hypoplasia, pulmonary stenosis, club feet, syndactyly, clinodactyly, micrognathia, genital anomalies and accessory spleens.
Pulmonary hypoplasia is due to mechanical effect of oligohydroamnios, which in turn is a consequence of renal dysfunction. Club foot is also common because of oligo or anhydramnios [3].
The locus for Meckel syndrome is on chromosome 17, long arm, region 2, and bands 1-4.
Phenotype variability and cases that did not have confirmed linkage to 17q suggests that there is some degree of locus heterogeneity.
Measurement of alpha fetoprotein levels in maternal serum or amniotic fluid after 12 weeks of gestation may help to detect encephalocele or any open neural tube defects. However, maternal serum or amniotic fluid fetoprotein level may be normal, in case a membrane covers the cephalocele [4].
MGS may demonstrate variations in phenotypic expression in addition to classical finding. The association of minor and infrequent features in MGS should be kept in mind while doing an autopsy so that it will not lead to misdiagnosis. This further helps us guide the patient about the issue of recurrence of anomalies in future pregnancies [5].
Since there is no treatment, it is preferable to diagnose the condition prenatally and abort the affected fetus.

Differential Diagnosis List

Final Diagnosis

Meckel Gruber syndrome (MGS)

URL:	https://eurorad.org/case/13644
DOI:	10.1594/EURORAD/CASE.13644
ISSN:	1563-4086