Lecithin-cholesterol acyltransferase is the name of an enzyme the body produces to help remove cholesterol from the body. Everyone needs some cholesterol to stay healthy but too much cholesterol is bad. Lecithin-cholesterol acyltransferasedeficiency or LCAT deficiency is an extremely rare genetic disease which comes in two types – familiar LCAT deficiency or FLT and fish-eye disease or FED.
As the common name suggests, the eyes are primarily affected and the condition could lead to blindness as a result. Patients with fish-eye disease may not start symptoms until their late teens or early adult years. Their parents will not show any symptoms but they both will carry the defective gene pair that causes the symptoms. This disease is so rare that there are thought to be only 125 people in the world to have it. Since it is so rare, not much is known about it.
Symptoms begin as the patient begins seeing small gray dots. These dots are actually clots of cholesterol on the cornea. The grey spots become more predominant until it looks like there are grey clouds in the patient’s eyes. The grey coloring reminded some doctors of boiled fish and so that is how the common name developed. The patient then gradually loses the ability to see and can eventually go blind.
Fish-eye disease occurs when the LCAT gene undergoes a mutation and becomes corrupted. Typically, the LCAT gene contains an enzyme that helps remove cholesterol from the blood and particular tissues. It carries out this mission by helping the cholesterol to bind to particular lipoproteins which carry the cholesterol to the liver. When the LCAT gene becomes corrupted, it is unable to perform this task, and cholesterol clouds the cornea of the eye. This clouding is visible, and the name comes from its resemblance to boiled fish eyes. Over time, clouding can severely impact visibility.
Fish-eye disease is inherited from parents in an autosomal recessive manner. This means that each parent is a carrier of one corrupted copy of the LCAT gene and one non-corrupted copy of the LCAT gene. If the child receives both corrupted copies of the gene, they have a 25% chance of developing fish-eye syndrome. Typically, carriers do not exhibit any signs of the genetic abnormality or suffer any of the symptoms associated with it. Symptoms usually appear in adolescence or early adulthood, and progress in severity over the sufferer’s life.
There is no cure for fish-eye disease. Since it’s so rare there is also no specific medication or treatment plan for fish-eye disease. However, becoming blind is not inevitable.
One surgical procedure that may help is corneal transplants, where the old cloudy cholesterol-covered corneas are removed and new ones from a recently deceased organ donor are put in place. It is unknown how permanent a solution is to fish-eye disease.
People with fish-eye disease and their parents need to be aware that they can pass this disease on to the next generation. Parents may need to discus with their doctors the risks of having more children. Patients should receive genetic counseling and genetic tests to make sure they carry the defective gene before they have children. Children of patients that have been born after symptoms developed should also receive gene tests.
Because of the way in which fish-eye disease is inherited, there is no way of preventing it. Genetic testing can alert someone that they are a carrier or at risk for developing it, as it would reveal the status of the LCAT gene.
While it cannot be prevented, it can be treated. Regular monitoring by an ophthalmologist is required, and some preliminary studies suggest that medications which reduce cholesterol may have a positive impact on the disease. As fish-eye disease is a progressive condition, it worsens over time, sometimes causing significant lack of vision. In severe cases, a corneal transplant is required to replace the affected cornea(s). Corneal transplants are one of the most common transplants performed.