Gaucher disease

Bone marrow aspiration	Hepatosplenomegaly

 

Alternative names

Glucosylceramide storage disease; GSDI

Definition

An inherited deficiency of an enzyme (ß-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 and risks 

Gaucher Disease is a rare, inherited, potentially fatal disorder. Deficiency of the enzyme ß-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 manifest the disease, but silently harbor one abnormal copy of the gene.

There are three forms of Gaucher Disease, Types 1, 2, and 3, that are recognized. They are classified by age of onset (infantile, juvenile, adult) and the presence or absence of neurological involvement.

• Type 1 disease is the most commonly seen form affecting 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 presents 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. The incidence of Types 2 and 3 diseases is 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.

Prevention 

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.

Symptoms

• bone pain and fractures
• easy bruising
• fatigue
• seizures

Signs and tests

• large spleen (splenomegaly)
• large liver (hepatomegaly)
• low blood count (anemia)
• low platelet count (thrombocytopenia)
• crossed eyes (strabismus)
• seizures
• abnormal gait (ataxia)  

Evaluation:

• 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:

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 pass Gaucher’s disease. By virtue of Gaucher’s disease being a recessive disease, offspring of two parental 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.

Treatment 

In the past the only potential treatment was removal of the spleen (splenectomy). This has given way to injections of a replacement synthetic enzyme (Cerezyme/Ceredase). Gene therapy is an experimental approach.

A novel oral treatment has recently been evaluated. This drug is known as N-butyldeoxynojirimycin (OGT 918). The mechanism of action is by inhibiting the formation of glucocerebroside. This trial improved key clinical features of Gaucher’s disease including liver and spleen size and, to a lesser degree, blood counts. The most frequent side effect was diarrhea. This is currently being further evaluated.

Prognosis

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 recombinant enzyme, most patients with the adult-chronic form can look forward to normal or near normal life expectancy.