Marble bone disease
Marble bone disease
Description, Causes and Risk Factors:
In healthy individuals, bones are constantly being broken down (resorption) by cells called osteoclasts, and new bone material is constantly being formed by cells called osteoblasts. marble bone disease when there is a failure in bone resorption. The mass of bone increases, but the new bone material that is added is porous, weak, and brittle.
Marble bone disease is a disease of unknown etiology, familial in occurrence, and characterized by an increase in the radiographic density of the bones, but with preservation of their structural contour.
The disease is hereditary, occurring sporadically, usually Mendelian recessive in character but occasionally dominant. Consanguineous marriages resulting in affect offspring have been reported, but no sexual or racial predisposition has been noted.
Reserchers beleive marble bone disease is caused by ineffective osteoclastic bone resorption resulting from mutations in the chloride channel 7 (ClCN7) gene. Individuals with marble bone disease have increased numbers of large ineffective osteoclasts in addition to increased serum total tartrate-resistant acid phosphatase (TRACP) activity.
In the benign type of numerous variations of the clinical picture also occur according to the extent of the disease, but most cases present with a fairly typical picture.
In malignant type the obliteration of the bone marrow soon leads to a severe anemia, extramedullary hematopoiesis soon leads to a severe anemia, extramedullary hematopoiesis and resulting enlargement of the liver and spleen. Hypocalcemic tetany can occur soon after birth. Optic atrophy, facial palsy, severe deafness, multiple fractures of the long bones, and mental retardation usually complete the clinical picture. The disease follows a malignant course and is usually fatal within months or a few years.
The condition is usually widespread throughout the skeletal system. On roentgenograms the bones appear almost homogeneous in consistency, and differentiation between compact and cancellous bone is absent. Progressive anemia, which is characteristically seen in the disease, is probably explained by the destruction of the bone marrow by the lime deposits. The base of the skull is frequently involved, and the foramina of exit for the cranial nerves are narrowed. This results in pressure on the cranial nerves, with such sequelae as facial palsy or paralysis, speech defects, deafness, optic atrophy, etc.
The adult form of marble bone disease affects approximately 1,250 people in the US. The most severe form, malignant marble bone disease, is very rare, affecting only 8 to 40 children born in the US each year. It is difficult to estimate how often the different forms of marble bone disease occur worldwide.
Symptoms may include:
Bones that break easily and do not heal properly.
Carpal tunnel syndrome.
Macrocephaly (abnormal enlargement of the head).
Enlargement of the liver, lymph glands, or spleen.
Failure to thrive (delayed growth, weight gain, and development).
Hydrocephalus (fluid on the brain).
Paralysis or loss of control of muscles in the face or eyes.
Hematological symptoms seldom occur, and a normal life span can be expected in most cases. Macrocephaly and enlargement of the mandible becomes evident in the teenage period, and the patient has a typical leonine appearance. Usually the patient grows very tall and some clubbing of the long bones, genu valgum and coxa vara can be observed. Proptosis due to thickening of the orbital bone can occur.
Recurrent acute facial nerve palsy, identical to Bell's palsy may occur in childhood. A conductive deafness become manifest within a few years due to bony involvement of the middle ear structure.
Marble bone disease is generally diagnosed through skeletal x-rays. X-rays of marble bone disease patients will have an unusual density with a chalky white appearance. Bone density tests and bone biopsies can confirm the diagnosis while other tests such at CAT scans or MRI can be performed to evaluate any potential complications.
Bone biopsy can confirm the diagnosis. Additional tests may be done to look for associated problems in vision, hearing, blood composition, and so forth.
It is not yet possible to reduce the progressive ossification in the benign type. The only successful measure so far has been exposing the compressed nerves. Both the adult and childhood forms of marble bone disease may benefit from Actimmune injections.
Bone marrow transplant is the only complete cure available for malignant marble bone disease. Bone marrow transplant has many risks, but if it is successful it saves the life of a child who would otherwise die from complications of the disorder.
Other treatments include nutrition, prednisone (helps improve the blood cell count), and physical and occupational therapy.
Surgical management of fractures and cranial nerve compression has been generally successful, although difficult due to the density of the bone.
Physical and occupational therapy can help children reach their full potential and adults to retain function and independence. Speech therapy is often needed in young children, because the heavy skeleton can cause language delays even in children of normal intelligence. Professional counseling can help children and their families cope with the emotional aspects of deformed features.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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