Otopalatodigital syndrome type 2

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Otopalatodigital syndrome type 2 is a disorder primarily involving abnormalities in skeletal development. It is a member of a group of related conditions called otopalatodigital spectrum disorders, which also includes otopalatodigital syndrome type 1, frontometaphyseal dysplasia, Melnick-Needles syndrome, and terminal osseous dysplasia. In general, these disorders involve hearing loss caused by malformations in the tiny bones in the ears (ossicles), problems in the development of the roof of the mouth (palate), and skeletal abnormalities involving the fingers or toes (digits). Otopalatodigital syndrome type 2 also tends to cause problems in other areas of the body, such as the brain and heart.

People with otopalatodigital syndrome type 2 have characteristic facial features including wide-set and downward-slanting eyes; prominent brow ridges; a broad, flat nose; and a very small lower jaw and chin (micrognathia). Affected individuals often have abnormalities of the fingers and toes, such as unusual curvature of the fingers (camptodactyly) and shortened or absent thumbs and big toes. People with otopalatodigital syndrome type 2 usually have short stature, abnormally curved (bowed) bones in the arms and legs, and other abnormal or absent bones. Underdeveloped ribs can cause problems with breathing in affected individuals. Some people with this condition have an opening in the roof of the mouth (a cleft palate) or hearing loss.

In addition to skeletal abnormalities, individuals with otopalatodigital syndrome type 2 may have developmental delay, increased fluid in the center of the brain (hydrocephalus), protrusion of the abdominal organs through the navel (omphalocele), heart defects, chest abnormalities, obstruction of the ducts between the kidneys and bladder (ureters), and, in males, opening of the urethra on the underside of the penis (hypospadias).

Males with otopalatodigital syndrome type 2 generally have much more severe signs and symptoms compared to affected females. Males with this condition typically do not survive past infancy because of respiratory failure due to an underdeveloped rib cage.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Otopalatodigital syndrome type 2 is caused by mutations in the FLNA gene. The FLNA gene provides instructions for producing the protein filamin A, which helps build the network of protein filaments (cytoskeleton) that gives structure to cells and allows them to change shape and move. Filamin A binds to another protein called actin, and helps the actin to form the branching network of filaments that make up the cytoskeleton. Filamin A also links actin to many other proteins to perform various functions within the cell.

The FLNA gene mutations that cause otopalatodigital syndrome type 2 all result in changes to the filamin A protein in the region that binds to actin. The mutations are described as "gain-of-function" because they appear to lead to a protein with an increased ability to bind to actin. Researchers believe that the mutations impair the stability of the cytoskeleton and disrupt cellular processes involved in skeletal development, but it is not known how changes in the protein relate to the specific signs and symptoms of otopalatodigital syndrome type 2.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an X-linked pattern. A condition is considered X-linked if the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes in each cell. In males, who have only one X chromosome, a mutation in the only copy of the gene in each cell is sufficient to cause the condition. In females, who have two copies of the X chromosome, one altered copy of the gene in each cell can lead to less severe features of the condition or may cause no signs or symptoms at all. A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Otopalatodigital syndrome type 2 is a rare disorder, affecting fewer than 1 in every 100,000 individuals. Its specific incidence is unknown.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Abnormal pinna morphology · Very frequent (99-80%)

An abnormality of the pinna, which is also referred to as the auricle or external ear.

Anodontia · Very frequent (99-80%)

The absence of all teeth from the normal series by a failure to develop.

Bowing of the long bones · Very frequent (99-80%)

A bending or abnormal curvature of a long bone.

Broad forehead · Very frequent (99-80%)

Width of the forehead or distance between the frontotemporales is more than two standard deviations above the mean (objective); or apparently increased distance between the two sides of the forehead.

Cleft palate · Very frequent (99-80%)

Cleft palate is a developmental defect of the palate resulting from a failure of fusion of the palatine processes and manifesting as a separation of the roof of the mouth (soft and hard palate).

Depressed nasal bridge · Very frequent (99-80%)

Posterior positioning of the nasal root in relation to the overall facial profile for age.

Downslanted palpebral fissures · Very frequent (99-80%)

The palpebral fissure inclination is more than two standard deviations below the mean.

Hearing impairment · Very frequent (99-80%)

A decreased magnitude of the sensory perception of sound.

Other findings in the same source

From: Orphanet

Additional reported features include Hypertelorism (Very frequent (99-80%)); Large fontanelles (Very frequent (99-80%)); Low-set ears (Very frequent (99-80%)); Malar flattening (Very frequent (99-80%)); Narrow chest (Very frequent (99-80%)); Narrow mouth (Very frequent (99-80%)); Oligodontia (Very frequent (99-80%)); Prominent supraorbital ridges (Very frequent (99-80%)); Short hallux (Very frequent (99-80%)); Short nose (Very frequent (99-80%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Otopalatodigital syndrome type 2 is Orthopaedics, with a orthopaedic specialist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• What explains the change in pain, movement or function?
• Which activities need adjustment while the diagnosis is being clarified?
• What are the roles of rehabilitation, observation and surgery in this situation?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Otopalatodigital syndrome type 2. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.