Congenital disorder of glycosylation type Ia (CDG-Ia) is an inherited metabolic disorder that impairs the production of glycoproteins, which are proteins that have attached carbohydrates. In CDG-Ia, there is a defect in an enzyme called phosphomannomutase.
CDG-Ia affects many systems of the body, notably the nervous system. The disease causes developmental delay that can lead to mental disability. It can also cause seizures and stroke-like episodes. It impairs both the ability to move physically and the ability coordinate that movement. Approximately 20% of infants with the disease die within the first year of life. Most people with CDG-Ia will be wheelchair bound.
A person with CDG-Ia may show some or all of the following symptoms: a failure to grow at the normal rate; a particular type of limited vision which leads to blindness (retinitis pigmentosa); an underactive thyroid (hypothyroidism); an enlarged liver and/or liver disease; heart and kidney problems; low blood sugar; a decreased ability for blood to clot following an injury; thickened, swollen, pitted skin (peau d'orange); and bone abnormalities. Some people have many of the above symptoms while others have few.
In people with CDG-Ia, certain distinct features are apparent at birth. These may include inverted nipples, poor muscle tone, almond shaped eyes which are crossed, a large forehead, an unusual distribution of body fat, and abnormal genitals. Part of the brain called the cerebellum is often partially wasted away. Females with the disease often do not reach sexual development.
CDG-Ia accounts for 70% of the congenital disorders of glycosylation, which combined affect 1 in every 50,000 to 100,000 births. Cases of CDG-Ia have been reported worldwide, with about half coming from Scandinavian countries.
There is no cure for CDG-Ia, however some measures may be taken to improve the lives of people affected by the disease. Parents of a young child with CDG-Ia should ensure the child gets the best possible nutrition to help with growth. Some children will require a feeding tube. Early use of occupational, physical, and speech therapy may be helpful in improving the child's long-term abilities in these areas. Surgical or non-surgical measures may correct crossed eyes and ensure better vision. Infusion of blood plasma may be necessary before a surgery to help clotting. Medications may help to control seizures. Various hormones may be useful if the person has an underactive thyroid gland. Wheelchairs and other movement aids are often useful as well.
Twenty percent of people with CDG-Ia die within the first year of life, often due to infection, liver problems, or heart disease. Others with CDG-Ia may live into adulthood. Most are wheelchair bound throughout their life. Some are able to speak and converse, albeit with some impairment. People with CDG-Ia are unable to live independently, but may accomplish certain tasks independently.
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