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Meckel-Gruber syndrome
This severe multisystem condition is typically diagnosed during pregnancy or shortly after birth. It is inherited in an autosomal recessive pattern and is associated with significant health challenges due to its impact on vital organ development.
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Overview
Meckel-Gruber syndrome (MKS) is a rare inherited disorder that affects the development of various organ systems in the body. It is classified as a ciliopathy, meaning it results from problems with cilia. Cilia are tiny, hair-like structures on the surface of most cells that play crucial roles in cell signalling, movement, and sensing the environment [PMID:24360907].
The condition is characterised by a specific combination of features, most commonly enlarged kidneys with cysts, a particular brain malformation called encephalocele (where brain tissue protrudes through a gap in the skull), and extra fingers or toes (polydactyly). Due to the severity of these developmental issues, Meckel-Gruber syndrome often leads to stillbirth or death shortly after birth. Its exact prevalence varies globally, with estimates ranging from 1 in 13,000 to 1 in 140,000 live births [PMID:28225556].
Symptoms & clinical features
The clinical features of Meckel-Gruber syndrome can vary, but a classic triad of symptoms is often observed. These include polycystic kidneys, which are enlarged and contain numerous fluid-filled sacs, leading to impaired kidney function. Another key feature is an encephalocele, typically located at the back of the head, where part of the brain protrudes through an opening in the skull.
Polydactyly, the presence of extra fingers or toes, is also a common characteristic. Other possible features include abnormalities of the liver, such as fibrosis or cysts, and sometimes developmental issues affecting the lungs, heart, or genitourinary system. Facial anomalies, such as a cleft lip or palate, may also be present in some individuals.
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Affected organs
Meckel-Gruber syndrome primarily affects several key organ systems. The kidneys are almost always involved, typically showing significant enlargement and cystic changes that severely impair their function. The central nervous system is also consistently affected, with encephalocele being a hallmark feature. Other brain abnormalities can sometimes be present.
Liver involvement is common, ranging from mild fibrosis to more severe cystic changes. The skeletal system is affected by polydactyly, often involving both hands and feet. Less frequently, developmental anomalies can occur in the lungs, heart, and reproductive organs, contributing to the broad clinical spectrum of the syndrome.
Risks & severity
Meckel-Gruber syndrome is considered a severe condition, and its prognosis is generally very poor. Most affected pregnancies result in stillbirth or neonatal death shortly after birth due to severe organ malformations, particularly kidney failure and brain abnormalities. The severity of the developmental anomalies directly influences the outcome.
There is a spectrum of presentation, but even in less severe cases, the multiple organ system involvement leads to significant health challenges. Due to the critical nature of the organ malformations, individuals with Meckel-Gruber syndrome do not typically survive beyond the perinatal period.
Genetic causes
Meckel-Gruber syndrome is caused by pathogenic variants (sometimes called mutations) in specific genes. These genes provide instructions for making proteins that are essential for the proper development and function of cilia, which are microscopic, hair-like structures found on the surface of many cells. These cilia play vital roles in cell communication and organ development.
Several genes have been identified as causative for MKS, with some of the most common including *CEP290*, *MKS1*, and *TMEM67* [PMID:21390449]. For instance, the *CEP290* gene provides instructions for a protein critical to the structure and function of cilia. When these genes contain pathogenic variants, the cilia do not form or function correctly, leading to the developmental abnormalities seen in Meckel-Gruber syndrome.
Inheritance pattern
Meckel-Gruber syndrome is inherited in an autosomal recessive pattern. This means that a child must inherit two copies of a pathogenic gene variant - one from each parent - to develop the condition. Individuals who inherit only one copy of a pathogenic variant are called carriers. Carriers typically do not show any symptoms of the condition themselves because they have one working copy of the gene.
If both parents are carriers of a pathogenic variant in the same gene associated with Meckel-Gruber syndrome, there is a 25% chance with each pregnancy that their child will inherit two copies of the variant and be affected by the syndrome. There is a 50% chance the child will be a carrier like their parents, and a 25% chance the child will inherit two working copies of the gene and not be affected or be a carrier.
When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.
Diagnosis & testing
Diagnosis of Meckel-Gruber syndrome is often suspected during pregnancy through routine prenatal ultrasound scans. These scans may reveal characteristic features such as enlarged, cystic kidneys, encephalocele, or polydactyly. Further imaging techniques, such as foetal MRI, may be used to confirm and further characterise the observed anomalies.
Definitive diagnosis is confirmed through genetic testing. This can be performed using samples obtained during pregnancy (e.g., chorionic villus sampling or amniocentesis) or from the affected infant after birth. Genetic testing looks for pathogenic variants in genes known to cause Meckel-Gruber syndrome. NHS Genomic Medicine Service laboratories can perform these tests; your clinical team would typically refer you to clinical genetics services for assessment and genetic testing (NHS R-codes for ciliopathies include R308, R310).
Management & lifestyle
Due to the severe nature of Meckel-Gruber syndrome and its typical perinatal lethality, management is primarily focused on accurate diagnosis and supportive care for the family. If a diagnosis is made during pregnancy, families will receive counselling from a specialist team, including obstetricians, genetic counsellors, and neonatologists, to understand the prognosis and discuss management options.
For pregnancies that continue to term, medical care would involve supportive measures for the infant, though the prognosis remains very poor. Families are offered genetic counselling to understand the inheritance pattern, recurrence risks for future pregnancies, and options for reproductive planning. There are currently no specific treatments to cure Meckel-Gruber syndrome.
UK care pathway
In the UK, if Meckel-Gruber syndrome is suspected, individuals and families are typically referred to their local NHS Clinical Genetics Service. Here, a team of specialists, including clinical geneticists and genetic counsellors, can provide comprehensive assessment, diagnostic testing, and support. Genetic testing for conditions like Meckel-Gruber syndrome is available through the NHS Genomic Medicine Service (GMS), often utilising specific national genomic test directories and R-codes (e.g., R308, R310 for ciliopathies).
Genetic counsellors play a vital role in explaining the condition, its inheritance pattern, implications for other family members, and reproductive options. They also offer psychological support and can signpost to relevant support groups.
Frequently asked questions
What is a ciliopathy?
A ciliopathy is a genetic disorder caused by problems with cilia. Cilia are tiny, hair-like structures on cells that act like antennae, helping cells communicate and function properly. When cilia don't work correctly, it can affect the development and function of many organs, leading to conditions like Meckel-Gruber syndrome.
How is Meckel-Gruber syndrome detected during pregnancy?
Meckel-Gruber syndrome is often detected during routine prenatal ultrasound scans. These scans can identify characteristic features such as enlarged, cystic kidneys, an encephalocele (a brain abnormality), and extra fingers or toes (polydactyly). If these features are seen, further investigations and genetic testing may be offered.
If we have one child with Meckel-Gruber syndrome, what is the chance of it happening again?
Since Meckel-Gruber syndrome is inherited in an autosomal recessive manner, if you have one affected child, it means both parents are carriers. In subsequent pregnancies, there is a 25% chance (1 in 4) for each child to be affected, a 50% chance to be a carrier, and a 25% chance to not be affected and not be a carrier.
Are there any treatments for Meckel-Gruber syndrome?
Unfortunately, there is currently no cure or specific treatment for Meckel-Gruber syndrome. Due to the severe nature of the organ malformations, the condition is typically fatal during pregnancy or shortly after birth. Management focuses on accurate diagnosis, genetic counselling, and supportive care for the family.
What kind of support is available for families affected by Meckel-Gruber syndrome?
Families affected by Meckel-Gruber syndrome receive support from multidisciplinary teams, including clinical geneticists, genetic counsellors, obstetricians, and neonatologists. Genetic counsellors provide information about the condition, discuss reproductive options, and offer psychological support. They can also help connect families with relevant patient support groups.
References
- McConnachie DJ, Stow JL, Mallett AJ. Ciliopathies and the Kidney: A Review. American journal of kidney diseases : the official journal of the National Kidney Foundation. 2021. PMID: 33039432
- Shaheen R, Szymanska K, Basu B. Characterizing the morbid genome of ciliopathies. Genome biology. 2016. PMID: 27894351
- Guo A, Chitayat D, Blaser S. Fetal syringomyelia. Acta neuropathologica communications. 2014. PMID: 25092126
- Hartill V, Szymanska K, Sharif SM. Meckel-Gruber Syndrome: An Update on Diagnosis, Clinical Management, and Research Advances. Frontiers in pediatrics. 2017. PMID: 29209597
- Nyberg DA, Hallesy D, Mahony BS. Meckel-Gruber syndrome. Importance of prenatal diagnosis. Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine. 1990. PMID: 2277397
- Gazioğlu N, Vural M, Seçkin MS. Meckel-Gruber syndrome. Child's nervous system : ChNS : official journal of the International Society for Pediatric Neurosurgery. 1998. PMID: 9579873
- Ahmed M, Fischer S, Robert KL. Cleavage of the Meckel-Gruber syndrome protein TMEM67 by ADAMTS9 uncouples Wnt signaling and ciliogenesis. Nature communications. 2025. PMID: 40436881
- Al-Belushi M, Al Ibrahim A, Ahmed M. A review of Meckel-Gruber syndrome--incidence and outcome in the state of Qatar. The journal of maternal-fetal & neonatal medicine : the official journal of the European Association of Perinatal Medicine, the Federation of Asia and Oceania Perinatal Societies, the International Society of Perinatal Obstetricians. 2016. PMID: 26333300