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Meester-Loeys syndrome
This X-linked syndrome is characterised by features such as joint hypermobility, developmental delays, and distinct facial characteristics. It mainly affects males and is caused by pathogenic changes in the BGN gene.
Overview
Meester-Loeys syndrome is a rare inherited condition primarily affecting connective tissues, which are essential for supporting and connecting other tissues and organs throughout the body. These tissues provide strength and elasticity, and when they are affected, it can lead to a range of symptoms. The condition is mainly observed in males, though females can be carriers and sometimes experience milder symptoms [PMID:27083074].
Clinical features often include musculoskeletal issues like joint laxity and curvature of the spine (scoliosis), along with developmental delays that can affect speech and motor skills. Individuals may also have specific facial features. The severity of Meester-Loeys syndrome can vary considerably among affected individuals.
Symptoms & clinical features
Individuals with Meester-Loeys syndrome often present with a combination of clinical features. Musculoskeletal symptoms are common and may include hypermobile joints, meaning joints that can extend beyond their usual range of motion. This can sometimes lead to joint instability or dislocations. Curvature of the spine, known as scoliosis, is also frequently observed [PMID:27083074].
Developmental delays are another key characteristic, which can impact a child's ability to reach motor milestones, such as sitting or walking, and may also affect speech development. Some individuals may have a high-arched palate or crowded teeth. Distinctive facial features can also be present, such as wide-set eyes (hypertelorism) and prominent ears. The specific symptoms and their severity can differ from person to person.
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Affected organs
Meester-Loeys syndrome primarily affects the connective tissues, which are found throughout the entire body. This wide distribution means that various organ systems can be impacted. The musculoskeletal system is prominently affected, leading to issues with joints and the spine. Connective tissue also plays a role in the structure of the face, contributing to some of the characteristic facial features seen in the syndrome.
While the main impact is on connective tissue, developmental delays suggest involvement in neurological development, although this is likely secondary to the overall genetic effect rather than direct organ damage. The eye structure, which relies on connective tissue, may also be subtly affected, though significant ocular problems are not typically a primary feature.
Risks & severity
Meester-Loeys syndrome is a rare condition, and its exact prevalence is not well established. The severity of the syndrome can range from relatively mild symptoms to more significant challenges affecting mobility and development. As an X-linked condition, males are typically more severely affected than females.
Developmental delays are a common concern, potentially affecting speech, motor skills, and cognitive development to varying degrees. The long-term outlook for individuals with Meester-Loeys syndrome often depends on the specific symptoms present and the level of support and interventions received. There isn't a universally defined age of onset, as some features like joint hypermobility might be noticeable in early childhood, while developmental delays become apparent as a child grows.
Genetic causes
Meester-Loeys syndrome is caused by pathogenic variants in the BGN gene, located on the X chromosome. The BGN gene provides instructions for making a protein called biglycan. Biglycan is a small proteoglycan, a type of protein that plays a crucial role in the structure and function of connective tissues [PMID:27083074].
Biglycan interacts with other components of the extracellular matrix - the network of proteins and other molecules that surrounds and supports cells. It is involved in regulating collagen fibril formation, which is essential for the strength and integrity of connective tissues. Pathogenic changes in the BGN gene lead to a dysfunctional or absent biglycan protein, disrupting the normal organisation and function of connective tissues, which gives rise to the features of Meester-Loeys syndrome [PMID:29397682].
- BGN biglycan
Inheritance pattern
Meester-Loeys syndrome has an X-linked recessive inheritance pattern. This means the BGN gene is located on the X chromosome, one of the two sex chromosomes. Males have one X chromosome and one Y chromosome, while females have two X chromosomes.
In X-linked recessive conditions, males are typically more severely affected because they only have one copy of the X chromosome. If their single X chromosome carries a pathogenic variant in the BGN gene, they will develop the condition. Females, having two X chromosomes, generally need pathogenic variants on both copies of the BGN gene to be significantly affected. However, female carriers (with one affected X chromosome) may sometimes experience milder symptoms due to a process called X-inactivation, where one of the two X chromosomes in each cell is randomly inactivated. For every pregnancy, a male with the condition will pass the pathogenic variant to all of his daughters, making them carriers, but none of his sons. A female carrier has a 50% chance of passing the pathogenic variant to each child; sons who inherit the variant will be affected, and daughters who inherit it will be carriers.
X-linked recessive: sons of a carrier mother have a 50% chance of being affected. Daughters have a 50% chance of being carriers.
Diagnosis & testing
A diagnosis of Meester-Loeys syndrome is often suspected based on the characteristic clinical features, such as joint hypermobility, developmental delays, and specific facial characteristics. Confirmation of the diagnosis typically involves genetic testing. Genomic testing can identify pathogenic variants in the BGN gene.
In the UK, genetic testing for conditions like Meester-Loeys syndrome is available through the NHS Genomic Medicine Service (GMS). Referral to a clinical genetics service is usually made by a GP or specialist, such as a paediatrician or a neurologist, who suspects a genetic condition. The GMS uses a national test directory, and tests for rare disease diagnosis, including BGN-related conditions, can be found under specific R-codes.
Management & lifestyle
Management of Meester-Loeys syndrome focuses on addressing the specific symptoms experienced by each individual. As it is a complex condition affecting multiple body systems, a multidisciplinary team approach is often beneficial. This team may include paediatricians, geneticists, orthopaedic specialists, physiotherapists, occupational therapists, and speech and language therapists.
Physiotherapy and occupational therapy can help manage joint hypermobility and improve motor skills. Speech and language therapy can support individuals with communication difficulties. Regular follow-up with medical professionals is important to monitor symptoms and provide appropriate interventions. Genetic counsellors can provide information about the condition, its inheritance pattern, and implications for family planning.
UK care pathway
In the UK, individuals suspected of having Meester-Loeys syndrome typically enter the NHS Genomic Medicine Service (GMS) pathway. A referral from a GP or specialist to a regional clinical genetics service is the usual first step. Genetic counsellors play a vital role in this pathway, offering support, information, and explaining the implications of genetic testing. Diagnostic testing for rare diseases is guided by the National Genomic Test Directory, using specific R-codes to ensure the correct genomic analysis is performed. This system helps ensure equitable access to genomic testing across the UK.
Frequently asked questions
How common is Meester-Loeys syndrome?
Meester-Loeys syndrome is considered a rare condition. The exact number of people affected is not precisely known, but it is not commonly encountered in the general population.
Can females be affected by Meester-Loeys syndrome?
Yes, females can be affected, but typically they are carriers of the pathogenic variant and may experience milder symptoms compared to males. Males are usually more severely affected due to the X-linked inheritance pattern.
Is there a cure for Meester-Loeys syndrome?
There is currently no cure for Meester-Loeys syndrome. Management focuses on treating the specific symptoms and providing support to improve quality of life through various therapies and medical interventions.
What kind of doctors treat Meester-Loeys syndrome?
Management often involves a team of specialists, including paediatricians, clinical geneticists, orthopaedic doctors for bone and joint issues, physiotherapists, occupational therapists, and speech and language therapists.
How is Meester-Loeys syndrome inherited?
Meester-Loeys syndrome is inherited in an X-linked recessive pattern. This means the gene responsible, BGN, is on the X chromosome. Males are generally more affected as they have only one X chromosome, while females with one affected X chromosome are typically carriers and may have milder symptoms.
References
- Meester JAN, De Kinderen P, Verstraeten A. Meester-Loeys Syndrome. Advances in experimental medicine and biology. 2021. PMID: 34807424
- Meester JAN, Hebert A, Bastiaansen M. Expanding the clinical spectrum of biglycan-related Meester-Loeys syndrome. NPJ genomic medicine. 2024. PMID: 38531898
- Riancho JA, Vega AI, Del Real A. A Family with Meester-Loeys Syndrome Caused by a Novel Missense Variant in the BGN Gene. International journal of molecular sciences. 2025. PMID: 41465473
- De Kinderen P, Rabaut L, Hebert A. Generation of an induced pluripotent stem cell (iPSC) line (BBANTWi009-A) from a Meester-Loeys syndrome patient carrying a BGN mutation. Stem cell research. 2023. PMID: 36599284
- Meester JAN, De Kinderen P, Verstraeten A. The role of biglycan in the healthy and thoracic aneurysmal aorta. American journal of physiology. Cell physiology. 2022. PMID: 35476501
- Mizumoto S, Kosho T, Yamada S. Pathophysiological Significance of Dermatan Sulfate Proteoglycans Revealed by Human Genetic Disorders. Pharmaceuticals (Basel, Switzerland). 2017. PMID: 28346368