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Cranioectodermal dysplasia (Sensenbrenner)
This condition is a ciliopathy, meaning it arises from issues with cilia, small cellular structures. It can lead to distinctive facial features, skeletal abnormalities, and problems with organs like the kidneys, typically presenting from infancy.
Overview
Cranioectodermal dysplasia, also known as Sensenbrenner syndrome, is a rare inherited condition that affects various parts of the body. It is classified as a ciliopathy, which means it results from problems with structures called cilia. These hair-like projections are found on the surface of nearly all human cells and play crucial roles in cell signalling and development [PMID:33650221]. Affected individuals often present with a combination of skeletal, hair, teeth, and kidney abnormalities.
The condition can manifest differently among individuals, but common features include a distinctive head shape, short stature, and sparse or fine hair. Cranioectodermal dysplasia typically becomes apparent in early childhood, with symptoms often noticed by parents or healthcare professionals during infancy.
Symptoms & clinical features
Individuals with cranioectodermal dysplasia present with a range of symptoms affecting multiple body systems. Skeletal features often include a long, narrow head (dolichocephaly) and a prominent forehead, along with shorter limbs and fingers. Many affected children have short stature. Dental problems can be significant, including widely spaced or abnormally shaped teeth, and late eruption of teeth.
Ectodermal features involve the hair, skin, and nails. Hair is typically sparse, fine, and brittle. Some individuals may also have problems with nail development. Kidney issues are also commonly observed, ranging from structural abnormalities to reduced kidney function over time, which can lead to chronic kidney disease [PMID:33650221]. Other potential features include vision problems, hearing loss, and in some cases, developmental delay.
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Affected organs
Cranioectodermal dysplasia primarily affects skeletal development, leading to abnormalities in bone growth, particularly in the skull and limbs. The ectodermal tissues are also significantly impacted, which includes structures like hair, teeth, and nails. The kidneys are frequently involved, with a risk of developing kidney cysts and progressive kidney disease.
Other organs that can be affected include the eyes, potentially leading to vision problems, and the ears, which may result in hearing difficulties. In some instances, the brain can be affected, contributing to developmental delays.
Risks & severity
The severity of cranioectodermal dysplasia can vary considerably between individuals, even within the same family. Key risks include the progression of kidney disease, which may necessitate medical management or, in severe cases, kidney transplant in later life. Skeletal abnormalities, particularly short stature, are common and can impact quality of life.
Developmental delays can range from mild to moderate, affecting motor skills and cognitive development in some children. Due to the rarity of the condition, exact prevalence figures are not well established. The age of onset is typically in infancy or early childhood, when many of the characteristic features become apparent.
Genetic causes
Cranioectodermal dysplasia is caused by pathogenic variants in genes that are important for the function of cilia, which are small, hair-like structures on the surface of cells. These genes include *IFT122*, *WDR19*, and *WDR35* [PMID:24076722]. The proteins produced from these genes are essential components of the intraflagellar transport (IFT) system, which is responsible for building and maintaining cilia.
Changes in these genes can disrupt the normal formation or function of cilia. Since cilia play critical roles in various cellular processes, including signalling pathways important for development, their dysfunction can lead to the wide range of symptoms seen in cranioectodermal dysplasia, affecting bone, hair, teeth, and kidney development.
- IFT122 intraflagellar transport 122
- WDR19 WD repeat domain 19
- WDR35 WD repeat domain 35
Inheritance pattern
Cranioectodermal dysplasia is inherited in an autosomal recessive pattern. This means that an individual must inherit two altered copies of the same gene - one from each parent - to develop the condition. If a person inherits only one altered copy and one normal copy, they are considered a carrier and typically do not show symptoms of the condition.
For two carrier parents, there is a 25% chance with each pregnancy that their child will inherit two altered copies of the gene and develop cranioectodermal dysplasia. There is a 50% chance the child will be a carrier, and a 25% chance the child will inherit two normal copies of the gene and not be affected. Family members of someone with cranioectodermal dysplasia may consider genetic counselling to understand their own carrier status and reproductive risks.
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 cranioectodermal dysplasia is often suspected based on the unique combination of clinical features, such as skeletal abnormalities, specific facial characteristics, and ectodermal findings. Imaging studies, such as X-rays, can help to confirm skeletal abnormalities, and kidney function tests can assess for renal involvement.
Confirmatory diagnosis relies on genetic testing to identify pathogenic variants in one of the associated genes (*IFT122*, *WDR19*, or *WDR35*). Genetic testing is typically requested by a clinical geneticist or specialist paediatrician and can be accessed through the NHS Genomic Medicine Service. The relevant NHS Genomic Medicine Service 'R' code for targeted gene testing for ciliopathies or specific syndromic conditions may apply.
Management & lifestyle
Management of cranioectodermal dysplasia focuses on addressing the specific symptoms and needs of each individual. This typically involves a multidisciplinary team of specialists, including paediatricians, clinical geneticists, nephrologists (kidney specialists), dentists, and orthopaedic surgeons.
Regular monitoring of kidney function is important, and kidney-related complications are managed as they arise. Dental care is crucial due to the common tooth abnormalities. Orthopaedic intervention may be considered for severe skeletal issues. Developmental support and therapies, such as physiotherapy or occupational therapy, may also be beneficial for some individuals. The management approach is guided by the NHS care pathway, aiming to optimise health and development.
UK care pathway
In the UK, individuals suspected of having a rare genetic condition like cranioectodermal dysplasia often enter the NHS Genomic Medicine Service pathway. Referrals are typically made by a GP or specialist paediatrician to a regional clinical genetics service. Here, a clinical geneticist can assess symptoms, arrange appropriate genetic testing - guided by NHS National Genomic Test Directory R-codes - and provide a diagnosis. Genetic counsellors are available to offer support and information about inheritance, testing options for family members, and what the diagnosis might mean for the individual and their family.
Frequently asked questions
What are cilia and why are they important in cranioectodermal dysplasia?
Cilia are tiny, hair-like structures found on almost all cells in the body. They act like cellular antennae, sending and receiving signals that are crucial for normal development and function of various organs. In cranioectodermal dysplasia, problems with cilia lead to the diverse range of symptoms observed.
If I have a child with cranioectodermal dysplasia, what are the chances of future children also being affected?
Since cranioectodermal dysplasia is inherited in an autosomal recessive pattern, if you and your partner both carry a genetic change for the condition, there is a 25% chance with each pregnancy that your child will be affected. Genetic counselling can provide a more personalised risk assessment.
Are there different types or severities of cranioectodermal dysplasia?
The severity of cranioectodermal dysplasia can vary, even within the same family, depending on which gene is affected and the specific genetic change. Some individuals may have milder symptoms, while others experience more significant health challenges, particularly concerning kidney function.
What kind of medical specialists will be involved in my child's care?
A multidisciplinary team is typical for cranioectodermal dysplasia. This often includes a clinical geneticist, paediatrician, nephrologist (kidney specialist), dentist, and potentially orthopaedic surgeons, ophthalmologists, and developmental therapists, depending on the specific symptoms.
Is there a cure for cranioectodermal dysplasia?
Currently, there is no cure for cranioectodermal dysplasia. Management focuses on treating the specific symptoms and providing supportive care to improve quality of life. Research into ciliopathies continues to explore potential new therapies.
References
- Walczak-Sztulpa J, Wawrocka A, Sikora W. WDR35 variants in a cranioectodermal dysplasia patient with early onset end-stage renal disease and retinal dystrophy. American journal of medical genetics. Part A. 2022. PMID: 35875935