Osteopetrosis

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Osteopetrosis is a rare bone disorder that is characterized by the bones turning harder and denser in nature. Find out all about this condition, including its causes, symptoms, diagnosis and treatment.

What is Osteopetrosis?

It is an uncommon congenital disorder that is characterized by dense bones. This occurs when the osteoclasts (cells involved in the decomposition and resorption of bone tissue) fail to reabsorb the bone resulting in imbalance between the bone formation and breakdown.

Osteopetrosis Synonyms

The condition is also known by various other names, such as:

Picture of Osteopetrosis

Picture 1 – Osteopetrosis

  • Stone bone
  • Marble bone disease
  • Albers-Schonberg disease

Osteopetrosis Types

The condition is differentiated into various types, which are as follows:

Malignant Osteopetrosis

This particular type is associated with problems like anemia. It is observed in infants and its symptoms arise shortly after birth. Some other symptoms of this disease are infections and vision problems.

Benign Osteopetrosis

This type of osteoporosis is more common in adults and is characterized by fractures at regular intervals. Another peculiar characteristic is that these are genetically dominant unlike Malignant Osteopetrosis. This is further classified into two more varieties – Type 1 and Type 2.

Intermediate Osteopetrosis

In this form, the symptoms are different from the two above mentioned types. The adverse effects are more severe and also appear at old age. This type has also been found to be recessive as no case has still been traced to any genetic association.

Carbon Anhydrase Type 2 deficiencies

This last type of the disease is caused due to deficiency of an enzyme CA2. This enzyme is associated with the functioning of bones, kidney and brain. It is characterized by frequent body fractures, hearing loss and other common symptoms of Osteopetrosis.

The classification for this disease is based on various factors, such as pattern of inheritance and symptoms of the disorder.

Osteopetrosis Causes

The disease is believed to be genetic. It is to be remembered that benign ostepetrosis is not genetic in nature unlike the other types of the disorder. This disease occurs due to problems related with osteoclasts. Osteoclasts are responsible for proper growth of the bone in the human body. These cells make it possible by achieving a balance between bone formation and bone resorption. In this condition, the number of osteoclasts in the body get altered thereby leading to changed functionality. Alternatively, the functioning of the osteoclasts may get affected due to the presence of a dysfunction.

The basic cause involves the interruption of the process of manufacture of acid by Osteoclasts on the bone surface. This interruption leads to reduced bone digestion which finally results in the development of the condition.

Osteopetrosis Symptoms

The symptoms of the disorder vary from one type to another. For instance, in case of mild osteopetrosis there are fewer fractures or none while in severe cases fractures are quite common.

Know about some of the common symptoms of the condition:

1)   The risk of fractures increase in this condition. The fractures do not heal easily. Fractures occur in the initial stages of the disease in adults.

2)   Blindness and problems related to hearing are also common, as the cranial nerves get affected.

3)   Hematological problems, such as anemia and infections, occur frequently.

4)   The overall growth of the body is also affected.

5)   The bones become denser and are referred to as marble bones.

6)   Facial paralysis may occur due to increased pressure on the nerves by the extra bone.

7)   Excessive bleeding may be observed due to platelet deficiency in the body.

Osteopetrosis Diagnosis

Diagnosis of this disease is done with the help of X-rays that help to find the problems related to bone density. Several other tests are used to diagnose the associated problems like problem in hearing and vision problems. The diagnosis can get delayed due to a number of reasons. The most common reason is the concern of parents about associated symptoms like hearing problems and blindness. As such, the tests for analyzing bone abnormalities are not performed by the doctor. Know about some of the common tests used for the diagnosis of this disorder:

X-rays

X-rays show lucent bands near the end of long bones. Fractures are also visible in the X-ray. In case of mild osteopetrosis, clubbing of metaphyses and increased bone density is observed.

Bone Marrow Examination

In order to find out the exact number of osteoclasts in the body, bone marrow examination is done. If the number of osteoclasts is abnormal (increase or decreased), the person might be suffering from osteopetrosis. There is only one exception here, which involves the mutation of TNFSF11 gene. Even in this condition, the number of osteoclasts gets reduced in the body.

CT scan

CT scan may be used in some cases.

As this disease is genetic in nature, the family history of a patient is also studied to get vital clues.

Osteopetrosis Differential Diagnosis

The differential diagnosis of this condition is very important as its symptoms are similar to other bone related disorders. A number of tests are performed to distinguish Osteopetrosis from conditions like:

  • Prostate cancer
  • Lead intoxication
  • Fluoride intoxication
  • Beryllium intoxication
  • Sickle cell anemia
  • Leukemia

Osteopetrosis Treatment

Know about the various techniques used for the treatment of this disease:

Image of Osteopetrosis

Picture 2 – Osteopetrosis Image

Hematopoietic Stem Cell Transplantation

The technique of hematopoietic stem cell transplantation is used for treating Malignant Osteopetrosis.  It is important that this transplantation should be performed at an early stage of the disease. In later stages, nerve damage may occur and transplantation might not be of much use then. In this process, the bone marrow from a healthy individual is transplanted to the patient. One of the key requirements for the transplantation to be successful is that the recipient should be free from any infection. Moreover, the HLA antigen of the donor and the recipient should also match.

Gamma Interferon Treatment

Another alternative option is gamma interferon treatment. This is useful when transplantation is not possible due to reasons like non-availability of a donor. Interferon is helpful in the bone degradation and thus initiating the bone degradation process may produce relief from the symptoms of the disease.

Antibiotics

Since infections are quite common in this disease, they should be treated as early as possible. For this purpose, suitable antibiotics should be used.

Iron Supplements

In order to treat the anemia produced by the disease, iron supplements may be provided to the patients. Similarly, in order to treat thrombocytopenia, thrombocytes may be given to the patient.

Surgery

In some case the spleen is also removed surgically in order to provide relief to the patient.

Orthopedic measures

In people suffering from Benign Osteopetrosis precautionary measures are suggested by the doctor to avoid chances of fractures. Orthopedic measures may be taken by the doctor for relieving the bone related problems.

The treatment of this condition not only involves use of medical measures but also effective care and monitoring. Parents should support their diseased children and encourage them regularly. They should also extend full cooperation to doctors during treatment to ensure greater comfort for their children.

References:

http://en.wikipedia.org/wiki/Osteopetrosis

http://www.osteopetrosis.org/

http://ghr.nlm.nih.gov/condition/osteopetrosis

http://www.patient.co.uk/doctor/Osteopetrosis.htm

http://rarediseases.about.com/od/rarediseaseso/a/osteopetrosis.htm

http://www.healthofchildren.com/N-O/Osteopetroses.html#b

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