Tarsal carpal coalition syndrome
Alternate names[edit | edit source]
TCC;NOG-related-symphalangism spectrum disorder
Definition[edit | edit source]
Tarsal carpal coalition syndrome (TCC) is a genetic condition characterized by fusion of the bones in the wrist (carpals), ankles (tarsals), and the fingers and toes (phalanges).
Epidemiology[edit | edit source]
This condition is very rare; however, the exact prevalence is unknown.
Cause[edit | edit source]
- Tarsal-carpal coalition syndrome is caused by mutations in the NOG gene, which provides instructions for making a protein called noggin.
- This protein plays an important role in proper bone and joint development by blocking (inhibiting) signals that stimulate bone formation.
- The noggin protein attaches (binds) to proteins called bone morphogenetic proteins (BMPs), which keeps the BMPs from triggering signals for the development of bone.
Gene mutations[edit | edit source]
- NOG gene mutations that cause tarsal-carpal coalition syndrome reduce the amount of functional noggin protein.
- With decreased noggin function, BMPs abnormally stimulate bone formation in joint areas, where there should be no bone, causing the bone fusions seen in people with tarsal-carpal coalition syndrome.
- Mutations in the NOG gene are involved in several disorders with overlapping signs and symptoms.
- Because of a shared genetic cause and overlapping features, researchers have suggested that these conditions, including tarsal-carpal coalition syndrome, represent a spectrum of related conditions referred to as NOG-related-symphalangism spectrum disorder (NOG-SSD).
Inheritance[edit | edit source]
This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.
Onset[edit | edit source]
Symptoms of the condition can become apparent in infancy, and they worsen with age.
Signs and symptoms[edit | edit source]
- In this condition, fusion at the joints between the bones that make up each finger and toe (symphalangism) can also occur.
- Consequently, the fingers and toes become stiff and difficult to bend.
- Stiffness of the pinky fingers and toes (fifth digits) is usually noticeable first.
- The joints at the base of the pinky fingers and toes fuse first, and slowly, the other joints along the length of these digits may also be affected.
- Progressively, the bones in the fourth, third, and second digits (the ring finger, middle finger, and forefinger, and the corresponding toes) become fused.
- The thumb and big toe are usually not involved.
- Affected individuals have increasing trouble forming a fist, and walking often becomes painful and difficult.
- Occasionally, there is also fusion of bones in the upper and lower arm at the elbow joint (humeroradial fusion).
- Less common features of tarsal-carpal coalition syndrome include short stature or the development of hearing loss.
Clinical presentation[edit | edit source]
For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed.
80%-99% of people have these symptoms
- Abnormality of the ankles
- Short stature(Decreased body height)
- Tarsal synostosis(Fused ankle bones)
30%-79% of people have these symptoms
- Carpal synostosis
- Proximal symphalangism of hands(Fused innermost hinge joints)
- Radial deviation of finger
- Short 1st metacarpal(Shortened 1st long bone of hand)
5%-29% of people have these symptoms
- Cubitus valgus(Outward turned elbows)
- Distal symphalangism of hands(Fused outermost bones of hand)
- Humeroradial synostosis(Fusion of upper and lower arm bones)
Diagnosis[edit | edit source]
Molecular Genetics Tests may include:
- Deletion/duplication analysis
- Sequence analysis of the entire coding region
- Targeted variant analysis
Treatment[edit | edit source]
- Although there is no specific treatment or cure for TCC, there may be ways to manage the symptoms.
- A team of doctors or specialists is often needed to figure out the treatment options for each person.
NIH genetic and rare disease info[edit source]
Tarsal carpal coalition syndrome is a rare disease.
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