Diseases and Disorders associated with Mosaicism

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There are many diseases and disorders that are associated with mosaicism, especially since there are two types; somatic and gonadal.  Mosaicism occurs from a mutation during development to only a certain group of cells, not every cell in the body.  Chial lists many somatic mosaic disorders, but the diseases and disorders discussed in this article will be neurofibromatosis, hemophilia, and Bloom syndrome. 

The National Institute of Neurological Disorders and Stroke says that neurofibromatosis are genetic disorders that create tumors to grow in the nervous syndrome.  The tumors start in the nerves and myelin shealth, which is that thin membrane that protects the nerves.  This can create other abnormalities, like skin changes and bone deformities.  30 to 50% of new cases happen through a mutation in the genes.  The difference between the two types, the doctor looks for skin changes, tumors, or bone abnormalities in a parent, sibling or child with type 1.

The symptoms for type 1 is shown before 10 years of age where light brown spots all over skin, two or more growth on the iris of the eye, tumor on the optic nerve, and abnormal development of the spine, skull bone, or tibia.  For type 2, slow-growing tumors are found on the eighth cranial nerves and is less common. Besides these tumors, a doctor would look for cataracts or any changes to the retina, or other nervous system tumors.  The tumors can be removed via surgery since some type 1 tumors may be cancerous.  MR1s can show tumors and surgery can be used to remove the tumors but can result in hearing loss.

Hemophilia is a rare blood disorder where the blood does not clot normally.  It is a genetically disorder passed from parents to child through genes.  These people born with the disorder have little to no clotting factor, which is a protein needed for normal blood clotting.  When a person gets a cut and begins to bleed, normally the clotting factors stick to platelets to stop the bleeding.  For those who are hemophiliacs, they do not have as many clotting factors, if any, so they may need injections of a clotting factor to stop bleeding.  There are two types of hemophilia, A and B.  Those with A are missing or have low levels of clotting factor VIII while those with B are missing or have low levels of clotting factor IX.  More people with hemophilia are type A and usually occur in males, according to National Heart Lung Blood Institute.

Bloom Syndrome is an autosomal recessive genetic disease, meaning that both parents must be carrier to pass it on to their children.  Those with Bloom’s Syndrome have a large amount of breaks along their chromosomes.  Some symptoms of Bloom’s Syndrome are short stature, a butterfly-shaped facial rash; some may have an intellectual disability, and a high pitched voice.  Also, they are at an increased risk for infections, respiratory illness, cancer and leukemia. 

There is no treatment for those with Bloom’s Syndrome but there is testing; carrier and prenatal screenings.  For the carrier screening, the test requires a blood sample and it is possible to find the specific gene change in Ashkenazi Jews with Bloom Syndrome.  The carrier frequency is 1 in 110 Ashkenazi Jews, says Yael Rosenberg, and the males with Bloom’s are usually infertile and some women with Bloom’s have fertility problems. 

These are only three of the many diseases and disorders that are considered mosaic, either somatic and gonadal, though there are many others.  Many of these diseases or disorders do not have an exact genetic cause located so there still is much research needed to be done. 

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