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Genetic and Rare Diseases Information Center (GARD)

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Congenital radio-ulnar synostosis

Other Names for this Disease
  • Radial-ulnar synostosis
  • Radio-ulnar synostosis
  • Radioulnar synostosis
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Is this a genetic disorder?

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What is congenital radio-ulnar synostosis?

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.[1] The condition is present in both arms (bilateral) in approximately 60% of cases.[2] Signs and symptoms depend on the severity of the abnormality and whether it is bilateral; affected individuals often have limited rotational movement of the forearm.[1][2] Pain is usually not present until the teenage years.[2] It 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.[1][3][2] Some cases appear to be inherited in an autosomal dominant manner.[3] Treatment may be conservative or involve surgery depending on the severity of the abnormality and the range of movement.[1]
Last updated: 9/24/2012

What causes congenital radio-ulnar synostosis?

Congenital radio-ulnar synostosis is caused by abnormal development of the forearm bones in 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, cardiac (heart), 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.[2][3]

In some cases, congenital radio-ulnar synostosis appears to be inherited in an autosomal dominant manner.[2] In an article published in 2000, the authors found that autosomal dominant radio-ulnar synostosis with amegakaryocytic thrombocytopenia was caused by mutations in the HOXA11 gene in 2 families.[3]
Last updated: 9/24/2012

How is congenital radio-ulnar synostosis inherited?

Congenital radio-ulnar synostosis appears to be inherited in an autosomal dominant manner in some cases.[2][3] This means that one mutated copy of the disease-causing gene in each cell is sufficient to cause the condition. The mutated gene may occur for the first time in an affected individual, or it may be inherited from an affected parent. Each child of an individual with an autosomal dominant condition has a 50% (1 in 2) risk to inherit the mutated copy of the gene.

Congenital radio-ulnar synostosis may also occur with a variety of other abnormalities and may be associated with a chromosome abnormality or genetic syndrome. In these cases, the inheritance pattern may depend upon that of the underlying genetic abnormality. Some genetic abnormalities that have been reported in association with this condition include Apert syndrome, Carpenter syndrome, arthrogryposis, Treacher Collins syndrome, Williams syndrome, Klinefelter syndrome, and Holt-Oram syndrome.[2]

Congenital radio-ulnar synostosis may also occur sporadically as an isolated abnormality, in which case the cause may be unknown.
Last updated: 9/24/2012