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Oral-facial-digital syndrome type VI (Varadi-Papp)
This syndrome is a type of ciliopathy, meaning it affects cellular structures called cilia. It typically presents in infancy with distinctive physical features and can include brain abnormalities. Diagnosis involves clinical assessment and genetic testing.
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Overview
Oral-facial-digital syndrome type VI (OFD6), also known as Varadi-Papp syndrome, is a rare inherited disorder primarily affecting the development of the face, oral cavity, and digits (fingers and toes). It is one of several types of oral-facial-digital syndromes, each with distinct features and genetic causes. OFD6 is classified as a ciliopathy, a group of conditions caused by dysfunction of cilia, which are microscopic, hair-like structures on the surface of cells that play crucial roles in cell signalling and development [PMID:33659223].
Individuals with OFD6 often have a characteristic combination of physical features, such as a cleft lip, a notched tongue, and extra or fused digits. Neurological involvement, particularly cerebellar abnormalities, is also a common feature. Due to its rarity, the exact prevalence of OFD6 is not well established.
Symptoms & clinical features
The symptoms of Oral-facial-digital syndrome type VI typically involve a triad of features affecting the oral cavity, face, and digits, accompanied by cerebellar hypoplasia. Oral features often include a cleft lip, a notched or lobed tongue with hamartomas (non-cancerous growths), and extra or missing teeth [PMID:28795599]. Some individuals may also have a high-arched palate.
Facial characteristics can include a broad nasal bridge, widely spaced eyes (hypertelorism), and a small jaw (micrognathia). Digital abnormalities frequently include polydactyly (extra fingers or toes), particularly postaxial polydactyly (on the little finger/toe side), and syndactyly (fused fingers or toes). A key distinguishing feature of OFD6 from other OFD types is the consistent presence of cerebellar hypoplasia, which means the cerebellum (the part of the brain controlling balance and coordination) is underdeveloped [PMID:28795599]. This can lead to developmental delay and issues with motor skills.
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Affected organs
The primary organs and systems affected in Oral-facial-digital syndrome type VI include structures of the head and face, the skeletal system (specifically the hands and feet), and the central nervous system. Within the oral cavity, the tongue, lips, and palate are commonly affected. Facial bone development can also be impacted, leading to characteristic facial features. The cerebellum, a vital part of the brain, is consistently underdeveloped in individuals with OFD6, influencing neurological function. Other organs are generally not primarily affected, though systemic complications may arise depending on the severity of overall features.
Risks & severity
Oral-facial-digital syndrome type VI presents with a variable spectrum of severity, though individuals typically exhibit a recognisable pattern of clinical features. The presence of cerebellar hypoplasia can lead to developmental challenges, including delays in motor milestones and intellectual development, the extent of which can differ between individuals. The physical malformations of the mouth, face, and digits are present from birth and can impact feeding, speech, and mobility.
While OFD6 is a rare condition, the specific combination of oral, facial, digital, and neurological features helps differentiate it from other types of oral-facial-digital syndromes. Long-term health outcomes depend on the specific manifestations and the degree of cerebellar involvement, requiring individualised medical and developmental support. There are no specific lifetime risk figures for complications beyond those directly related to the developmental anomalies present.
Genetic causes
Oral-facial-digital syndrome type VI is caused by pathogenic variants in specific genes. The genes currently known to be associated with OFD6 are *OFD1* and *TMEM216* [PMID:28795599]. Both of these genes provide instructions for making proteins that are important for the structure and function of primary cilia.
*OFD1* encodes a protein involved in the formation and maintenance of centrioles and basal bodies, which are essential components of cilia. *TMEM216* codes for a transmembrane protein that localises to the transition zone of cilia, a critical region for regulating what enters and leaves the cilium. When these genes have pathogenic variants, the resulting dysfunctional proteins disrupt normal ciliary structure or function, leading to the developmental abnormalities seen in OFD6. This disruption of ciliary function explains why OFD6 is classified as a ciliopathy.
- OFD1 OFD1 centriole and centriolar satellite protein
- TMEM216 transmembrane protein 216
Inheritance pattern
Oral-facial-digital syndrome type VI 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. People who carry one altered copy of the gene are known as carriers; they typically do not show symptoms of the condition themselves because their other unaffected copy of the gene can compensate.
If both parents are carriers of a pathogenic variant in the same gene associated with OFD6, there is a 1 in 4 (25%) chance with each pregnancy that their child will inherit two altered copies and develop the condition. There is a 2 in 4 (50%) chance their child will be a carrier like them, and a 1 in 4 (25%) chance their child will inherit two unaffected copies and not be a carrier. Genetic counselling can provide more detailed information for affected families.
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 Oral-facial-digital syndrome type VI is typically suspected based on a constellation of characteristic clinical features, including the specific oral, facial, and digital abnormalities, coupled with evidence of cerebellar hypoplasia. Imaging studies, such as an MRI of the brain, are often used to confirm the presence and extent of cerebellar involvement.
Genetic testing is used to confirm the diagnosis and identify the specific pathogenic variants in genes like *OFD1* or *TMEM216*. This can be performed through gene panel testing that includes known OFD-related genes, or broader genomic tests like whole exome sequencing. In the NHS Genomic Medicine Service, relevant R-codes for such testing may include those for ciliopathies or intellectual disability, depending on the predominant clinical presentation, allowing clinicians to request appropriate genetic investigations.
Management & lifestyle
Management for individuals with Oral-facial-digital syndrome type VI is supportive and multidisciplinary, addressing the specific symptoms and developmental needs. This typically involves a team of specialists, which may include paediatricians, neurologists, geneticists, speech and language therapists, occupational therapists, and dentists.
Interventions may include surgical correction for cleft lip and palate, dental care for oral anomalies, and therapies to support developmental progress, particularly for motor skills and speech. Regular neurological assessments may be necessary to monitor for any changes related to cerebellar involvement. Management plans are individualised and evolve as the child grows, focusing on maximising functional independence and quality of life.
UK care pathway
In the UK, individuals suspected of having Oral-facial-digital syndrome type VI would typically be referred to a clinical genetics service. This service can provide a comprehensive clinical assessment, arrange appropriate genetic testing, and offer genetic counselling. Genetic testing in the NHS Genomic Medicine Service follows specific pathways, guided by national Genomic Test Directories and PanelApp recommendations. Referrals usually come from a general practitioner or another specialist paediatrician.
Clinical geneticists and genetic counsellors are key in guiding families through the diagnostic process, explaining inheritance patterns, and discussing implications for current and future family members. They can also help coordinate care with other specialist teams involved in managing the condition.
Frequently asked questions
What does 'autosomal recessive' inheritance mean?
Autosomal recessive inheritance means a child must inherit two altered copies of a specific gene, one from each parent, to develop the condition. Parents who each carry one altered copy of the gene usually do not show symptoms themselves.
What is a ciliopathy?
A ciliopathy is a genetic disorder caused by problems with cilia. Cilia are tiny, hair-like structures on the surface of most cells that play vital roles in cell signalling and development, and their dysfunction can affect many different body systems.
Will my child's development be affected?
Developmental delays, especially in motor skills, are common in OFD6 due to cerebellar hypoplasia. The extent of these delays can vary significantly between individuals. Early intervention therapies can be very beneficial.
Is there a cure for Oral-facial-digital syndrome type VI?
Currently, there is no cure for Oral-facial-digital syndrome type VI. Management focuses on addressing the specific symptoms and developmental needs of each individual through various medical and therapeutic interventions to improve quality of life.
What kind of doctors will be involved in my child's care?
Your child's care team will likely include a range of specialists such as a paediatrician, neurologist, clinical geneticist, speech and language therapist, occupational therapist, and dentist, among others, to address their specific needs.