Gaucher disease; GSDI
Gaucher disease is an inherited deficiency of the enzyme -glucosidase, which results in the buildup of a toxic substance (glucosylceramide) in different parts of the body, such as the spleen, liver, and bones.
Causes, incidence, and risk factors
Gaucher Disease is a rare, inherited, potentially fatal disorder. Deficiency of the enzyme -glucocerebrosidase leads to an accumulation of glucosylceramide in storage compartments (lysosomes) of certain cells in the body.
It is the most common type of a group of diseases known as lysosomal storage diseases. Lysosomes are cell compartments in which substances are broken down by specific enzymes. This is analogous to a machine breakdown at an assembly plant causing a huge pileup of unfinished products.
Deficiency of this enzyme causes the lysosomes to become congested with glucosylceramide. These congested lysosomes buildup in the liver, spleen, bones, and bone marrow. This, in turn, leads to decreased production of red blood cells (anemia), and thinning of the bones (osteopenia).
It is an autosomal recessive disease. This means that an affected child would inherit two abnormal copies of the enzyme, one from the mother and one from the father. The parents are known as carriers since they do not have the disease, but silently harbor one abnormal copy of the gene.
There are three recognized forms of Gaucher Disease - Types 1, 2, and 3. They are classified by age of onset (infantile, juvenile, adult) and the presence or absence of neurological (nervous system) involvement.
- Type 1 disease is most common. It affects both children and adults. It is most prevalent in the Ashkenazi Jewish population, affecting anywhere from 1 out of 500-1,000 births. Type 1 disease is characterized by the lack of neurologic involvement.
- Type 2 disease usually begins in infancy with severe neurologic involvement. This form, in addition to spleen and bone marrow damage, causes seizures and damage to the central nervous system (CNS). Central nervous system symptoms include: abnormal gait (ataxia), paralysis of eye muscles (ophthalmoplegia), and dementia.
- Type 3 disease typically has mild neurologic involvement and runs a slower, more favorable course. Types 2 and 3 disease occur in 1 out of every 50,000 to 100,000 births. The juvenile form can begin in childhood, often the teens, and cause spleen, bone marrow, and neurologic damage.
- bone pain and fractures
- easy bruising
Signs and tests
- large spleen (splenomegaly)
- large liver (hepatomegaly)
- low blood count (anemia)
- low platelet count (thrombocytopenia)
- crossed eyes (strabismus)
- abnormal gait (ataxia)
- blood cell examination for decreased enzyme activity
- white blood cell cultures for beta-glucosidase
- bone marrow aspiration
- biopsy of the spleen
- MRI, CT and/or X-ray of the skeleton
Genetic testing is performed by obtaining bone marrow or blood. Tests are designed to assess enzyme functional activity and/or obtain and sequence DNA to look for certain mutations.
Genetic testing is an extremely complicated personal decision that should be considered for a variety of reasons, including to advise siblings or other relatives in families of diagnosed patients, or to confirm a diagnosis in a patient with symptoms.
Testing can also determine if parents carry the gene that could cause Gaucher’s disease. Because Gaucher’s disease is a recessive disease, offspring of parents who are both carriers have a 25% chance of inheriting two abnormal copies of the gene.
Testing is complicated by the fact that the disease expression is extremely variable, and patients that test positive may not show signs and symptoms of the disease.
Therefore, routine testing is not recommended and may be disadvantageous, as this information may have to be revealed to insurance companies. A prenatal test can also tell if the fetus has Gaucher syndrome.
In every circumstance, genetic counseling should be available to anyone considering genetic testing for this disease.
In the past, the only treatment was removal of the spleen (splenectomy). Now, injections of a replacement synthetic enzyme (Cerezyme/Ceredase) are available. Gene therapy is an experimental approach.
A new oral treatment has recently been evaluated and is still under investigation. The drug, known as N-butyldeoxynojirimycin (OGT 918), works by inhibiting the formation of glucocerebroside. In clinical trials, patients had improved liver and spleen size and, to a lesser degree, improved blood counts. The most frequent side effect was diarrhea.
The infantile form of Gaucher disease may lead to early death. Most affected children die before the age of 5 years. With the availability of synthetic enzyme, most patients with the adult-chronic form can look forward to normal or near-normal life expectancy.
- bone infarctions
Calling your health care provider
Call your health care provider or a Comprehensive Gaucher Center if you have a family history of Gaucher disease. Screening may be reasonable for individuals of appropriate ethnic groups known to be at a higher risk of the disease.
Genetic counseling is recommended for prospective parents with a family history of Gaucher disease. Testing can determine if parents carry the gene that could pass on the Gaucher disease. A prenatal test can also tell if the fetus has Gaucher syndrome. Decision-making is complicated by the availability of effective treatments and ongoing therapeutic advances.
by Janet G. Derge, M.D.