Relation to other rare genetic disorders
Recent findings in genetic research have suggested that a large number of genetic disorders, both genetic syndromes and genetic diseases, that were not previously identified in the medical literature as related, may be, in fact, highly related in the genetypical root cause of the widely varying, phenotypically-observed disorders. Thus, PCD is a ciliopathy. Other known ciliopathies include Bardet–Biedl syndrome, polycystic kidney and liver disease, nephronophthisis, Alström syndrome, Meckel–Gruber syndrome and some forms of retinal degeneration. Diagnosis
Several diagnostic tests for this condition have been proposed. These include nasal nitric oxide levels as a screening test, light microscopy of biopsies for ciliary beat pattern and frequency and electron microscopic examination of dynein arms, as the definite diagnosis method. Genetic testing has also been proposed but this is difficult given that there are multiple genes involved. Classification
When accompanied by the combination of situs inversus (reversal of the internal organs), chronic sinusitis, and bronchiectasis, it is known as Kartagener syndrome (only 50% of primary ciliary dyskinesia cases include situs inversus). Treatment
There are no standardized effective treatment strategies for the condition. Current therapies for PCD are extrapolated from Cystic Fibrosis and patients with non-CF bronchiectasis and lack validation for PCD-specific use. Severe fatal respiratory failure can develop; long-term treatment with macrolides such as clarithromycin, erythromycin and azithromycin has been empirically applied for the treatment of primary ciliary dyskinesia in Japan, though controversial due to the effects of the medications. Prognosis
There is no reliable estimate of life expectancy for people with PCD.
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.