This has been shown to generate a net leftward flow in mouse and chick embryos, and sweeps the protein to the left, triggering normal asymmetrical development.However, in some individuals with PCD, mutations thought to be in the gene coding for the key structural protein left-right dynein (lrd) result in monocilia which do not rotate. There is therefore no flow generated in the node, Shh moves at random within it, and 50% of those affected develop situs inversus, which can occur with or without dextrocardia, where the laterality of the internal organs is the mirror-image of normal. Affected individuals therefore have Kartagener syndrome. This is not the case with some PCD-related genetic mutations: at least 6% of the PCD population have a condition called situs ambiguus or heterotaxy, where organ placement or development is neither typical (situs solitus) nor totally reversed (situs inversus totalis) but is a hybrid of the two. Splenic abnormalities such as polysplenia, asplenia and complex congenital heart defects are more common in individuals with situs ambiguus and PCD, as they are in all individuals with situs ambiguus.The genetic forces linking failure of nodal cilia and situs issues and the relationship of those forces to PCD are the subject of intense research interest. However, knowledge in this area is constantly advancing.
The largest multi-center study of lung function in people with PCD across many European countries found strong evidence refuting a common assumption that it is a mild disease. This study found that lung function of people with PCD is comparable to those with cystic fibrosis in childhood but is better in young adulthood. Both diseases, however, are progressive and lung function declines with age relative to peer groups. Survey data indicate that respiratory symptoms increase progressively and continuously beginning in the mid-20s relative to the population norm. History
The classic symptom combination associated with PCD was first described in 1904 by A. K. Siewert, while Manes Kartagener published his first report on the subject in 1933. The disorder is often now referred to as Siewerts syndrome or Siewert-Kartagener syndrome. References
Further reading
GeneReview/NCBI/NIH/UW entry on Primary Ciliary Dyskinesia


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