Description, Causes and Risk Factors:
Meckel-Gruber Syndrome is an autosomal recessive disease characterized by occipital encephalocele, cystic Kidneys and polydactyly. Other frequently associated anomalies include congenital hepatic fibrosis and hepatic cysts, and abnormal genitalia (cryptorchidism). The disease is invariably fatal at birth due to pulmonary hypoplasia and renal failure.
Incidence of Meckel-Gruber syndrome is 1:140,000 to 1:13,250, more common among Yemenite Jews. Risk of recurrence is 25% and carrier frequency is 1:56. History of affected siblings may be there. Parent consanguinity has been reported which supports evidence for autosomal recessive inheritance of this disorder. Mo consistent abnormality in Meckel's syndrome is renal dysplasia. Renal cysts are frequently large and the probably originate from the collecting ducts.
Autosomal recessive inheritance is well confirmed and the gene locus has been mapped to chromosome 17q21-24 by genome wide linkage study. The locus was later refined to within a less than 1 cM region (17q22), in which most of the Finnish MKS patients share a common chromosomal haplotype suggesting one major and relatively old mutation. However, in most of the non-Finnish MKS families studied, this linkage could not be confirmed. The linkage studies provide evidence that more than one locus is involved in bringing about the combination of CNS malformations, cystic kidneys, and polydactyly, maybe even in typical cases of MKS.
Genetics: MKS exhibits autosomal recessive inheritance. To date, five MKS genes have been identified (MKS1, TMEM67/MKS3, CC2D2A, RPGRIP1L and CEP290). The MKS1 gene encodes the Meckel syndrome type 1 protein (MKS1), which is predicted to have a role in ciliogenesis and renal tubulogenesis
Common symptoms of the disorder include a large soft spot with a bulging brain and spinal fluid and polydactyly (extra fingers and toes). The disorder also causes cysts to form in the kidneys, which will lead to large kidneys that do not function properly. In the majority of cases, the liver and lungs do not develop properly during fetal development, which will lead to breathing complications.
Alpha-fetoprotein (AFP) level from either maternal blood or amniotic fluid may help to detect an encephalocele in patients with Meckel-Gruber syndrome . AFP can be measured in amniotic fluid after about 12 weeks' gestation and in maternal blood after about 15 weeks' gestation.
Chromosome analysis is essential to exclude trisomy 13, which Meckel-Gruber syndrome mimics. Trisomy 13 carries a 1% recurrence risk, as opposed to the 25% recurrence rate for Meckel-Gruber syndrome. Linkage or mutation analysis is not yet available.
If anomalies are detected early in the first trimester, chorionic villus sampling (CVS) can be performed at 10-12 weeks' gestation or later in pregnancy if oligohydramnios does not permit amniocentesis.
Cardiac repair or neurosurgical intervention for encephalocele may be warranted in patients with Meckel-Gruber syndrome. Airway establishment may be difficult; thus, follow the guidelines provided by the American Society of Anesthesiologists.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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