Meckel Syndrome, Type 9

Alternative Names

  • MKS9
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WHO-ICD-10 version:2010

Congenital malformations, deformations and chromosomal abnormalities

Other congenital malformations

OMIM Number

614209

Mode of Inheritance

Autosomal recessive

Gene Map Locus

17p11.2

Description

Meckel Syndrome, type 9 is an extremely rare and fatal subset of MKS.  Similar to other MKS subtypes, the ciliopathy is characterized by the triad of occipital encephalocele, polydactyly and renal and biliary ductal dysplasia.  Other features may include an enlarged abdomen, short limbs, club feet, absent bladder and ambiguous external genitalia in males.  The disorder is congenital and often results in perinatal death.  MKS affects between 1/13250 to 1/140,000 live births and has a higher prevalence in populations such as Finns, Belgians, Gujrati Indians and Kuwaiti Bedouins.

Diagnosis can be made antenatally by ultrasound examination and genetic analysis can be carried out by chorionic villus sampling.  Treatment is mainly symptomatic and supportive as there is currently no cure for MKS.  Affected families may also benefit from genetic counselling.

Molecular Genetics

MKS9 follows an autosomal recessive pattern of inheritance.  It is caused by mutations in the B9D1 gene, which encodes a ciliary protein involved in protein localization, cilium assembly and Sonic hedgehog signaling.  The gene is also predicted to play a role in in-utero embryonic development.  Mutations in the B9D1 gene associated with MKS9 mainly include homozygous and compound heterozygous insertions and deletions.

Epidemiology in the Arab World

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Other Reports

Saudi Arabia

Al-Hamed et al. (2016) evaluated 44 Saudi families with antenatal ultrasound findings of bilateral cystic kidney disease, echogenic kidneys or enlarged kidneys in an attempt to identify the underlying genetic defects.  In one such family, the ultrasound investigation found bilaterally enlarged multicystic dysplastic kidneys, posterior encephalocele and bilateral clubfeet.  Genetic screening of 90 renal genes helped uncover a novel homozygous mutation (c.508_510delCTC, p.L170del) in the B9D1 gene of the proband.  In-silico analysis predicted the mutation to be deleterious and disease causing.  The case resulted in fetal death.  The parents were consanguineous and had one unaffected child who was found to be heterozygous for the B9D1 mutation.  

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