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North Carolina macular dystrophy (NCMD) is an inherited eye disorder that affects the development of the macula, the small, but important part of the eye located in the center of the retina. The macula allows a person to see fine details and do tasks that require central vision, such as reading and driving. It is also important for seeing colors. The severity of changes in the development of the macula varies, causing some people to have little or no vision loss, while others may have severe vision loss. NCMD is considered non-progressive, which means most researchers believe the vision loss does not change after birth. Others believe it may progress slowly through age twelve. However, vision loss may increase if complications develop, such as new, abnormal blood vessels growing under the retina (choroidal neovascularization).
NCMD is caused by changes (mutations) in a region of chromosome 6 (MCDR1 locus), as well as in a region of chromosome 5 (MCDR3 locus). Although there is no cure for NCMD, treatment may include low vision aids such as glasses with high powered lenses, large print reading material, and computer software that can turn text into speech.
Source: GARD Last updated on 05-01-20
The main symptom of North Carolina macular dystrophy (NCMD) is blurred central vision with normal color vision, although some people do have problems with color vision as well. Vision loss can range from very mild to very severe. Both eyes are usually affected the same. For the most part, vision loss does not get worse over time, although some researchers suggest it may be slowly progressive through age 12.
Findings on eye exam also vary and can be classified into three different grades depending on severity of changes that occurred during the development of the macula and related parts of the eye. It is important to remember a person with NCMD is born with these changes, rather than these changes developing throughout a person's lifetime. The Grades may be described as:
New blood vessels may also develop in the choroid (choroidal neovascularization) later in life, although this is not common. The choroid is a layer of nerves and blood vessels under the retina. The retina needs a healthy choroid to work. The abnormal growth of blood vessels in the choroid can damage the retina causing increased vision loss.
Last updated on 05-01-20
In most families, North Carolina macular dystrophy (NCMD) is caused by changes in a specific area (locus) of chromosome 6, called the MCDR1 locus. However, other families with NCMD have been found to have changes in the MCDR3 locus on chromosome 5. Genetic changes that cause a disease used to be called mutations, but now are more commonly called pathogenic variations.
The way a pathogenic variation in the genetic locus causes NCMD can be hard to understand. In many genetic diseases, the change in the DNA that causes the disease is in a gene, and in these cases, the pathogenic variation changes the instructions (code) for making the gene's protein. But medical researchers believe the pathogenic variations that cause NCMD are in non-coding areas of the DNA. These regions of the DNA may control when the proteins are made from other nearby genes (gene expression). In fact in 2016, medical researchers found that pathogenic variations in the MCDR1 locus are in non-coding regions close to the PRDM13 gene. The protein made from the PDRM13 gene is believed to be important for macular development. However, it is too early to tell if the pathogenic variations in the MCDR1 locus are changing the expression of the PRDM13 gene. Similarly, studies in 2017 suggest the MCDR3 locus is also involved in controlling when other genes are turned on (gene expression). At present researches believe the changes in the MCDR3 locus that cause NCMD may be affecting the expression of the IRX1 gene. But again it is too early to be certain.
Last updated on 05-01-20
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