Gaucher disease is a hereditary condition that causes a wide variety of complications, including osteoporosis. This article focuses on recovering bone health in this complicated disease.
What is Gaucher disease?
About one out of every 15 people of Eastern European Jewish descent carries at least one gene for Gaucher disease. Up to 60 percent of Ashkenazi Jews carry at least one gene for the condition. There are also non-Jewish populations in Sweden and in the Middle East that have more than the expected number of genes for Gaucher. Osteoporosis and other bone problems are most common in the slower-moving type 3 form of the disease.
What does Gaucher disease do to bone?
Defective white blood cells migrate to bone and dissolve it with some of the same inflammatory substances they use to destroy dead cells. They can also get "stuck" and die in bone. As they accumulate in bone, the toxic waste products they were unable to process also accumulate in the bone. The resulting skeletal manifestations of Gaucher disease are among the most disabling aspects of the condition. Gaucher disease in the bone tends to be:
- Focal, causing smaller lesions of osteonecrotic, dead bone, then
- Local, causing loss of bone mineral mass in long bones, and then,
- General, causing loss of bone mineral density (osteopenia) and fragility fractures (osteoporosis) all over the body.
Unlike most other forms of osteoporosis, secondary osteoporosis caused by Gaucher disease is not limited to the wrist, hip, and spine. And it doesn't just cause fractures.
About 20 percent of Gaucher's patients suffer loss of mobility. Bone pain is common. Children who have Gaucher's may present a "bone pain crisis," in which Gaucher cells in the bone marrow prevent proper blood circulation. There can be intense pain and fever for a few hours, or a few days, or a few weeks. In adolescents, Gaucher disease may present itself as the Erlenmeyer flask deformity. This gives bones a narrow neck that leads to a sloping, wide base, like the laboratory flask of the same name. In teens and adults, Gaucher may cause bone tissue death (necrosis) as accumulating Gaucher cells cut off circulation. Areas of dead bone may collapse, breaking the bone, or causing continuous joint pain and muscle spasms. The accumulation of defective cells can cause "pathological fractures" (corresponding to the "fragility fractures" of other forms of osteoporosis) that break bones without detectable impact. Bones sometimes break on their own.
What can be done about bone problems in Gaucher disease?
The first line of pharmaceutical therapy for bone problems in primary osteoporosis, the kind of brittle bone disease most common in women past the age of menopause, is hormone replacement therapy, HRT. The first line of drug therapy for bone problems in Gaucher disease is enzyme replacement therapy, ERT. The replacement enzyme is called imiglucerase. First found in the ovaries of Chinese hamsters, this enzyme is manufactured with genetically engineered bacteria and marketed as Cerezyme. There is a newer enzyme called velaglucerase alfa (VPRIV) that is made from cultures of human cells, and a still newer product called taliglucerase alfa (Elelyso) that is made from biologically engineered carrots.
Sometimes Gaucher patients receiving ERT develop an "allergic" reaction to the enzyme therapy. They are treated, paradoxically, with a corticosteroid drug like hydrocortisone (which usually causes fractures in bone) plus antihistamines to help the patient withstand the ERT. Gaucher patients may also be given an inhibitor drug to block the action of another enzyme, glucosylceramide synthase, which the harmful cells use to make their toxic chemicals. Glucosylceramide synthase inhibitors include eliglustat (marketed as Cerdelga) and miglustat (marketed as Zavesca).