What are the other Names for this Condition? (Also known as/Synonyms)

• Radial-Ulnar Synostosis
• Radioulnar Synostosis
• Radio-Ulnar Synostosis

What is Congenital Radio-Ulnar Synostosis? (Definition/Background Information)

• Congenital Radio-Ulnar Synostosis is a rare condition in which there is an abnormal connection (synostosis) of the radius and ulna (bones in the forearm) at birth. The condition is present in both arms (bilateral) in approximately 60% of cases
• Signs and symptoms depend on the severity of the abnormality and whether it is bilateral; people with the condition often have limited rotational movement of the forearm. Pain is usually not present until the teenage years
• There are 2 types of  - type 1 and type 2
  • In type 1, the fusion involves 2-6 cm of the area between the radius and ulna bones which is closer to the elbow; and, the knobby end of the radius that meets the elbow is absent (radial head)
  • In type 2, the fusion is farther from the elbow and there is dislocation of the radial head
• Both types result in a limitation of inward roll (pronation) and outward roll (supination) of the forearm, and in type 2 there is also a restriction of extension at the elbow
• Congenital Radioulnar Synostosis is due to abnormal fetal development of the forearm bones, but the underlying cause is not always known. It is sometimes a feature of certain chromosome abnormalities or genetic syndromes. Some cases appear to be inherited in an autosomal dominant manner
• Treatment may be conservative or involve surgery depending on the severity of the abnormality and the range of motion

(Source: Congenital Radio-Ulnar Synostosis; Genetic and Rare Disease Information Center (GARD) of National Center for Advancing Translational Science (NCATS), USA.)

Who gets Congenital Radio-Ulnar Synostosis? (Age and Sex Distribution)

• Congenital Radio-Ulnar Synostosis is a rare congenital disorder. The presentation of symptoms may occur at birth
• Both males and females may be affected
• Worldwide, individuals of all racial and ethnic groups may be affected

What are the Risk Factors for Congenital Radio-Ulnar Synostosis? (Predisposing Factors)

• A positive family history may be an important risk factor, since Congenital Radio-Ulnar Synostosis can be inherited in isolation, or as part of a syndrome
• Currently, no other risk factors have been clearly identified for the disorder

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Congenital Radio-Ulnar Synostosis? (Etiology)

• Congenital Radioulnar Synostosis is caused by abnormal development of the forearm bones during the fetal period, although the underlying cause of the developmental abnormality is not always known
• The condition may be isolated (occur without other abnormalities) or it may be associated with various other skeletal, heart (cardiac), neurologic, or gastrointestinal abnormalities
• When other abnormalities are present, the condition may be due to an underlying genetic cause, including a variety of syndromes or chromosome abnormalities. In these cases, the inheritance pattern may depend upon that of the underlying genetic abnormality
• Some chromosome abnormalities that may include Radioulnar Synostosis are:
  • Klinefelter syndrome
  • XXXY syndrome
• Examples of genetic syndromes that may include Radioulnar Synostosis are:
  • Apert syndrome
  • Crouzon syndrome
  • Carpenter syndrome
  • Arthrogryposis
  • Treacher Collins syndrome
  • Williams syndrome
  • Amegakaryocytic thrombocytopenia
  • Holt-Oram syndrome
• Congenital Radioulnar Synostosis appears to be inherited in an autosomal dominant manner in some cases
• It may also occur sporadically as an isolated abnormality, in which case the cause may be unknown

(Source: Congenital Radio-Ulnar Synostosis; Genetic and Rare Disease Information Center (GARD) of National Center for Advancing Translational Science (NCATS), USA.)

Autosomal dominant: Autosomal dominant conditions are traits or disorders that are present when only one copy of the mutation is inherited on a non-sex chromosome. In these types of conditions, the individual has one normal copy and one mutant copy of the gene. The abnormal gene dominates, masking the effects of the correctly function gene. If an individual has an autosomal dominant condition, the chance of passing the abnormal gene on to their offspring is 50%. Children, who do not inherit the abnormal gene, will not develop the condition or pass it on to their offspring.

What are the Signs and Symptoms of Congenital Radio-Ulnar Synostosis?

The signs and symptoms of Congenital Radio-Ulnar Synostosis may vary among affected individuals in type and severity.

• Dislocated radial head
• Limited elbow extension
• Radioulnar Synostosis

(Source: Congenital Radio-Ulnar Synostosis; Genetic and Rare Disease Information Center (GARD) of National Center for Advancing Translational Science (NCATS), USA.)

How is Congenital Radio-Ulnar Synostosis Diagnosed?

Congenital Radio-Ulnar Synostosis is diagnosed on the basis of the following information:

• Complete physical examination
• Thorough medical history evaluation
• Assessment of signs and symptoms
• Laboratory tests
• Imaging studies
• Biopsy studies, if necessary
• Molecular genetic testing to check for or confirm genetic mutations, when Congenital Radio-Ulnar Synostosis is part of a genetic syndrome

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Congenital Radio-Ulnar Synostosis?

The complications of Congenital Radio-Ulnar Synostosis may include:

• Severe problems with inward and outward movement of arms as well as elbows
• Pain associated with movement
• Nerve damage due to surgery
• Recurrence of the condition after treatment to repair the synostosis

Complications may occur with or without treatment, and in some cases, due to treatment also.

How is Congenital Radio-Ulnar Synostosis Treated?

• Congenital Radioulnar Synostosis may be treated with surgery
• Surgery is more commonly performed in patients who have bilateral Radioulnar Synostosis and/or patients who have very limited movement due to the radioulnar synostosis

(Source: Congenital Radio-Ulnar Synostosis; Genetic and Rare Disease Information Center (GARD) of National Center for Advancing Translational Science (NCATS), USA.)

How can Congenital Radio-Ulnar Synostosis be Prevented?

Congenital Radio-Ulnar Synostosis may not be preventable, since it is a genetic disorder.

• Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy), if available, may help in understanding the risks better during pregnancy
• If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
• Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders
• Regular medical screening at periodic intervals with tests and physical examinations are recommended

What is the Prognosis of Congenital Radio-Ulnar Synostosis? (Outcomes/Resolutions)

• The prognosis of Congenital Radio-Ulnar Synostosis is dependent upon the severity of the signs and symptoms and associated complications, if any
• Individuals with mild conditions have better prognosis than those with severe symptoms and complications
• Typically, the prognosis may be assessed on a case-by-case basis

Additional and Relevant Useful Information for Congenital Radio-Ulnar Synostosis:

The following DoveMed website link is a useful resource for additional information:

http://www.dovemed.com/diseases-conditions/rare-disorders/