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Gaucher Disease

Gaucher disease is an inherited disorder of metabolism where a type of fat (lipid) called glucocerebroside cannot be adequately degraded. Normally, the body makes an enzyme called glucocerebrosidase that breaks down and recycles glucocerebroside - a normal part of the cell membrane. People who have Gaucher disease do not make enough glucocerbrosidase. This causes the specific lipid to build up in the liver, spleen, bone marrow and nervous system interfering with normal functioning.

Gaucher disease occurs in about 1 in 50,000 to 1 in 100,000 individuals in the general population.

Symptoms

Symptoms of Gaucher disease vary greatly among those who have the disorder. The major clinical symptoms include:

  • Enlargement of the liver and spleen (hepatosplenomegaly).
  • A low number of red blood cells (anemia).
  • Easy bruising caused by a low level of platelets (thrombocytopenia).
  • Bone disease (bone pain and fractures).

Other symptoms depend on the type of Gaucher disease, which has three major types.

Type 1 is the most common, does not affect the nervous system and may appear early in life or adulthood. The symptoms in Type 2 and Type 3 Gaucher disease include those of Type 1 and other problems involving the nervous system such as eye problems, seizures and brain damage. In Type 2 Gaucher disease, severe medical problems begin in infancy. These individuals usually do not live beyond age two. There are also some patients with Type 2 Gaucher disease that die in the newborn period, often with severe skin problems or excessive fluid accumulation (hydrops). Individuals with Type 3 Gaucher disease may have symptoms before they are two years old, but often have a more slowly progressive disease process and the extent of brain involvement is quite variable. They usually have slowing of their horizontal eye movements.

Causes

Gaucher disease is caused by changes (mutations) in a single gene called GBA. Mutations in the GBA gene cause very low levels of glucocerebrosidase. A person who has Gaucher disease inherits a mutated copy of the GBA gene from each of his/her parents.

This condition is inherited in an autosomal recessive pattern.

Diagnosis

The diagnosis of Gaucher disease is based on clinical symptoms and laboratory testing. A diagnosis of Gaucher disease is suspected in individuals who have bone problems, enlarged liver and spleen (hepatosplenomegaly), changes in red blood cell levels, easy bleeding and bruising from low platlets or signs of nervous system problems.

Laboratory testing involves a blood test to measure the activity level of the enzyme glucocerebrosidase. Individuals who have Gaucher disease have very low levels of this enzyme activity. This type of testing is 90 percent accurate. A second type of laboratory test involves DNA analysis of the GBA gene for the four most common GBA mutations as well as several more rare mutations. Both enzyme and DNA testing can be done prenatally. A bone marrow or liver biopsy is not necessary to establish the diagnosis.

When the specific gene mutation causing Gaucher disease is known in a family, DNA testing can be used to accurately identify carriers. However it is often not possible to predict the patient's clinical course based upon DNA testing.

Treatment

Enzyme replacement therapy is now available as an effective treatment of individuals who have Gaucher disease. The treatment involves giving a modified form of the enzyme, glucocerbrosidase, by intravenous infusion every two weeks. Enzyme replacement therapy helps to stop progression and often reverse the symptoms of Gaucher disease, but does not affect the nervous system involvement.

A type of oral therapy which blocks the enzyme that makes the lipid is also available and clinical trials are still being conducted on this treatment.

Other treatments that may be required include: removal of the spleen (splenectomy); blood transfusions; pain medications; and joint replacement surgery.

 

Source

National Human Genome Research Institute, USA