Adult and infantile Gaucher disease in one family: mutational studies and clinical update

The Lysosomal Diseases Testing Laboratory: A review of the past 47 years

Lysosomal disorders are diseases that involve mutations in genes responsible for the coding of lysosomal enzymes, transport proteins, activator proteins and protein processing enzymes. These defects lead to the storage of specific metabolites within lysosomes resulting in a great variety of clinical features depending on the tissues with the storage, the storage products and the extent of the storage. The methods for rapidly diagnosing patients started in the late 1960's when the enzyme defects were identified eliminating the need for tissue biopsies. The first requests for diagnostic help in this laboratory came in 1973. In that year, patients with Krabbe disease and Niemann-Pick type A were diagnosed. Since that time samples from about 62 000 individuals have been received for diagnostic studies, and 4900 diagnoses have been made. The largest number of diagnosed individuals had metachromatic leukodystrophy and Krabbe disease because of our research interest in leukodystrophies. A number of new disorders were identified and the primary defects in other disorders were clarified. With new methods for diagnosis, including newborn screening, molecular analysis, microarrays, there is still a need for biochemical confirmation before treatment is considered. With new treatments, including gene therapy, stem cell transplantation, enzyme replacement used alone or in combination becoming more available, the need for rapid, accurate diagnosis is critical.

Gaucher's disease: a review

OBJECTIVE

To review the epidemiology, pathophysiology, clinical features, diagnosis, and treatment of Gaucher's disease, focusing on the role of enzyme replacement therapy.

DATA SOURCES

A MEDLINE search (from 1984 to July 1995) of English-language literature pertaining to the treatment of Gaucher's disease was performed. Additional references were obtained by reviewing the references of pertinent articles identified through the search. Tertiary sources were also used.

STUDY SELECTION AND DATA EXTRACTION

Articles with information on enzyme treatment were selected for review. Articles containing other interesting aspects of the disease or its treatment were also included.

DATA SYNTHESIS

Gaucher's disease is the most common lipid storage disorder known and results from a genetic deficiency of the enzyme glucocerebrosidase (glucosylceramidase). Enzyme deficiency results in accumulation of glucocerebroside within the reticuloendothelial system. It may present with hepatosplenomegaly, bone marrow suppression, and bone lesions. The most common of the three subtypes, type 1, is non-neuronopathic. In the rare neuronopathic subtypes, type 2 or 3, there may also be nerve cell destruction within the central nervous system with acute brainstem dysfunction or progressive neurologic deterioration, respectively. In 1991, enzyme treatment became available with the marketing of alglucerase, a placentally derived modified form of glucocerebrosidase. In 1994, a recombinant DNA modified form of glucocerebrosidase, known as imiglucerase, was developed to replace alglucerase. Most published data on enzyme therapy are with alglucerase in patients with type 1 disease. A dosage regimen of 60 units/kg every 2 weeks for moderately to severely ill patients has been effective in reducing hepatosplenomegaly, improving anemia and thrombocytopenia, as well as improving weight gain and growth in children and increasing vigor and self-esteem in adults. Bone involvement is often slow to respond to therapy although pain is frequently improved. Controversy exists as to whether lower dosage regimens are as effective. The role of enzyme therapy in the rarer neuronopathic subtypes remains to be determined, but initial reports have been disappointing.

CONCLUSIONS

Enzyme replacement therapy is available for the treatment of type 1 Gaucher's disease, resulting in clinical improvement with enhanced quality of life within the first year of treatment, although improvement in bone disease can take longer. Doses of 60 units/kg every 2 weeks are of clinical benefit to patients with moderate to severe disease. A number of lower dosage regimens have been evaluated in small groups of patients, with satisfactory clinical responses occurring in some of these patients.