MECKEL-GRUBER SYNDROME

• Lethal autosomal recessive syndrome.
• 25% recurrence rate. It is therefore important to distinguish from sporadic occipital encephaloceles which carry a 1-3% recurrence rate.
• This condition is autosomal recessive and has been mapped to chromosome bands 17q21-q24

ULTRASOUND

Major Criteria (1-3)

At least two major criteria are required to make the diagnosis.

1. Occipital Encephalocele (80%).
2. Bilateral Renal Cystic Dysplasia (95%).
• Kidneys enlarged 10-20 times.
• Hyperechoic and contain multiple, small 2-5mm cysts.
• Oligohydramnios (due to the dysplastic kidneys).
3. Postaxial Polydactyly of both the hands and feet (75%) (3).

ASSOCIATED MALFORMATIONS

• Renal: Agenesis, hypoplasia, ureteral duplication.
• Face : Cleft lip and palate, micrognathia and micropthalmos.
• Ambiguous genitalia.
• Abdomen: Congenital hepatic fibrosis, intestinal malrotation
• CNS : Dandy Walker Malformation (4).
• CVS : ASD, VSD, aortic hypoplasia, aortic stenosis, rotational anomalies

PROGNOSIS

Most fetuses are stillborn or die within the first day of life due to the pulmonary hypoplasia that results from the oligohydramnios. Prolonged survival up to 28 months has been reported (5). A rare case of survival of a fetus with Meckels Syndrome Variant has been reported (6).

DIFFERENTIAL DIAGNOSIS

Trisomy 13 - 15-30 % have cystic kidneys, however the concurrent presence of CNS abnormalities favors the diagnosis of trisomy 13.

REFERENCES

1. Naidich TP, Altman NR, Braffman BH et.al. Cephaloceles and related malformations. Am J Neuroradiol 1992;13:655-690.
2. Nyberg DA, Hallesy D, Mahony BS et.al. Meckel-Gruber Syndrome. Importance of prenatal diagnosis. J Ultrasound Med 1990;9:691-696.
3. Moerman PH, Verbeken E, Fryns JP et.al. The Meckel Syndrome. Pathological and cytogenetic observations in eight cases. Hum Genet 1982;62:240.
4. Herriot R, Hallman LA, Gray ES. Dandy Walker malformation in Meckels syndrome. Am J Med Genet 1991;39:207-210.
5. Ramadani HM, Nasrat HA. Prenatal diagnosis of recurrent Meckel syndrome. Int J Gynecol Obstet 1992;39:327-332.
6. Kaplan M, Ben-Neriah Z, Achiron R. Survival in an infant with a prenatally diagnosed Meckel syndrome variant. Am J Perinatol 1993;10:172-174.