Osteomalacia
May 26th, 2008 Posted by: admin
Definition
Osteomalacia is softening of the bones, caused by not having enough vitamin D, or by problems with the metabolism (breakdown and use) of this vitamin. These softer bones have a normal amount of collagen that gives the bones its structure, but they are lacking in calcium.
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Osteomalacia in children is known as rickets, and because of this, osteomalacia is often restricted to the milder, adult form of the disease.
Pathology
Osteomalicia is commonly found in confined, dark-skinned, or diet-disbalanced subjects.
Many of the effects of the disease overlap with the more common osteoporosis, but the two diseases are significantly different. Osteomalacia is a defect in mineralization of the protein framework known as osteoid. Osteoid is the bone protein matrix, composed primarily of type 1 collagen. When there is insufficient mineral or osteoblast dysfunction, the osteoid does not mineralize properly, and it accumulates. This defective mineralization is mainly caused by lack in vitamin D.
When the newly formed bone of the growth plate does not mineralize, the growth plate becomes thick, wide and irregular. This results in the clinical diagnosis of rickets, and is seen only in children because adults no longer have growth plates. When the remodeled bone does not mineralize, osteomalacia occurs, and this happens in all ages. Most of the hereditary causes of osteomalacia appear during childhood and cause rickets.
Osteomalacia is derived from Greek: osteo refers to bone, and malacia means softness. In the past, the disease was also known as malacosteon and its Latin-derived equivalent, mollities ossium.
Causes
There are numerous causes of osteomalacia. In children, the condition is called rickets and is usually caused by a deficiency of vitamin D.
Conditions that may lead to osteomalacia include:
- Not enough vitamin D in the diet
- Not enough exposure to sunlight, which produces vitamin D in the body
- Malabsorption of vitamin D by the intestines
Other conditions that may cause osteomalacia include:
- Hereditary or acquired disorders of vitamin D metabolism
- Kidney failure and acidosis
- Phosphate depletion associated with not enough phosphates in the diet (In adults, partial deficiency of alkaline phosphatase causes osteomalacia, bone pain and stress fractures. Patients also suffer from arthritis and chondrocalcinosis, as well as dental abnormalities.)
- Cancer
- Side effects of medications used to treat seizures
- Liver disease
Use of very strong sunscreen, limited exposure of the body to sunlight, short days of sunlight, and smog are factors that reduce formation of vitamin D in the body.
Risk factors for osteomalacia are related to the causes. In the elderly, there is an increased risk among people who tend to remain indoors and those who avoid milk because of lactose intolerance.
Symptoms
- Diffuse bone pain, especially in the hips
- Muscle weakness
- Bone fractures that are caused by very little trauma
Symptoms associated with low calcium including:
- Numbness around the mouth
- Numbness of extremities
- Spasms of hands or feet
- Abnormal heart rhythms
Investigastions and Tests
Your doctor may ask you to do the following invesigations if you are suspected to have osteomalacia:
- Bone biopsy
- Serum vitamin D level (may be low)
- Serum calcium levels
- Serum phosphate levels
- Bone x-ray
- Bone mineral density scan (DEXA)
Other tests may be done to determine if there is a renal problem or any other underlying disorder. These tests include:
Treatment
The treatment depends on the type of osteomalacia and of te causes that lead to it.
Oral supplements of vitamin D, calcium, and phosphorus may be given depending on the underlying cause of the disorder. Larger doses of vitamin D and calcium may be needed for people with intestinal malabsorption.
Monitoring the blood levels of phosphorus and calcium may be needed for people with certain underlying conditions.
Prevention
Osteomalacia resulting from vitamin D deficiency can be prevented in adults by eating enough dairy products that have extra vitamin D, and getting enough sunlight.
Prognosis
Improvement in the condition of the bones, shown by bone X-rays, can be seen within a few weeks in some people with vitamin deficiency disorders. Complete healing with treatment takes place in 6 months.