What is osteomalacia?
Osteomalacia is a condition affecting bones and muscles. It only occurs in adults. The bones become soft and prone to pain and fractures. It occurs when there is inadequate or defective bone mineralisation. This means that the bones are not hardened by mineral containing calcium and phosphate.
In children, where the bones are still growing, the same condition is called rickets. (See separate leaflet called ‘Rickets’ for more information.)
Osteomalacia is not the same as osteoporosis. In osteoporosis, the bones are less dense. This means there is less bone mass, but the amount of mineral in the bones is normal. (See separate leaflet called ‘Osteoporosis’ for more information.)
What causes osteomalacia?
Osteomalacia is usually caused by a lack of vitamin D (vitamin D deficiency). (See separate leaflet called ‘Vitamin D Deficiency’ for more information.)
Vitamin D regulates the bone-building process and the way the body handles calcium and phosphate which are used in the formation of strong, hard bones.
Vitamin D deficiency is actually very common, but it must be severe and prolonged for osteomalacia to develop. The lack of vitamin D also leads to muscle weakness, which is also part of osteomalacia.
Most of our vitamin D is made in the body by the action of sunlight on the skin. This means that people who stay inside or who cover up their skin, struggle to make enough vitamin D. Black and Asian people need more sunlight exposure to their skin to make vitamin D. The elderly and housebound are particularly at risk. Lack of sunlight on the skin is the main reason that people get vitamin D deficiency and osteomalacia.
Very little vitamin D is found in our food, although some foods do contain a little. Examples of foods relatively rich in vitamin D include: oily fish (such as herring, sardines, pilchards, salmon, tuna and mackerel) and egg yolk. Some of our foods are fortified with vitamin D, such as infant formula milk, margarine and some cereals.
Certain groups of people need more vitamin D than others. For example, pregnant and breast-feeding women. Some medical conditions and some medicines increase the likelihood of vitamin D deficiency and consequent osteomalacia.
There are some rare inherited conditions that affect bone mineralisation and cause osteomalacia. Aluminium poisoning is another rare cause.
How common is osteomalacia?
We don’t know exactly how common osteomalacia is. Possibly it is underdiagnosed, or not recognised enough in people who have symptoms such as bone pain. We know that vitamin D deficiency (which can lead to osteomalacia) is very common in the UK – it affects about 1 in 6 adults overall, and as many as 9 in 10 adults of South Asian origin.
Who gets osteomalacia?
Mostly, people get osteomalacia because they have a severe and prolonged lack of vitamin D. The groups of people most at risk of this problem are:
- Pregnant or breast-feeding women (because much of their vitamin D goes to the baby).
- People who get very little sunlight on their skin such as those who stay indoors a lot, or cover up when outside. This group includes the housebound, those who have been in hospital for a long time, people who wear veils such as the burqa or niqab, and people who adhere to strict sunscreen use.
- People with dark coloured skin (because less sunshine gets through the skin).
- People over 65 years old. The elderly tend to have thinner skin which means there is less fat/cholesterol in it to be turned into vitamin D by the sun.
- People with conditions that affect the way the body handles vitamin D. For example, those with coeliac disease, Crohn’s disease, some types of liver and kidney disease, and after surgery on the stomach (gastric surgery).
- Rarely, some people without any other risk factors or diseases become deficient in vitamin D. It is not clear why this occurs. It may be due to a subtle metabolic problem in the way vitamin D is made or absorbed. So, even some otherwise healthy, fair skinned people who get enough sun exposure can become deficient in vitamin D.
- People taking certain medicines: carbamazepine, phenytoin, primidone, barbiturates and some HIV treatments.
What are the symptoms of osteomalacia?
Sometimes the symptoms are very vague, with a general sense of not being well, and aches or pains. A common symptom is bone pain which comes on gradually and stays. This pain is often in the lower back and hips. But, in severe cases, all the bones may be aching and painful.
Other symptoms that may develop include:
- Bone tenderness – bones can feel painful to moderate pressure (often more noticeable in the ribs or shin bones). Not uncommonly, people have a hairline fracture in the bone which is causing tenderness and pain.
- Muscle weakness, often noticed as difficulty in climbing stairs or when getting up from the floor or a low chair. Sometimes, people who have osteomalacia walk in a ‘waddling’ pattern because of the muscle weakness.
How is osteomalacia diagnosed?
Osteomalacia may be suspected from your medical history, symptoms, or lifestyle (risk factors for vitamin D deficiency). A blood test can check your vitamin D levels. Liver function blood tests and calcium and phosphate levels are also measured as they may detect problems with the liver or bone that are linked to osteomalacia. Sometimes osteomalacia shows up on an X-ray, but X-rays are not usually necessary.
Usually, the symptoms plus blood tests are enough to make the diagnosis. Extra tests may be needed if the cause of the osteomalacia is in doubt, or if there are other vitamin or mineral deficiencies. For example, if anaemia is found as well, you should have a blood test to look for coeliac disease. More tests may be needed if you have another medical condition which is contributing to the problem.
How is osteomalacia treated?
The usual treatment is to take vitamin D supplements. This is a form of vitamin D called ergocalciferol or calciferol. Rarely, if osteomalacia is not caused only by vitamin D deficiency, other treatments may be needed.
Vitamin D can be given as an injection or as a medicine (liquid or tablets). Your doctor will discuss the dose, and best treatment schedule, depending on your situation, age, severity of the deficiency, etc. Briefly, one of the following may be advised
A single small injection of vitamin D will last for about six months. This is a very effective and convenient treatment. It is useful for people who do not like taking medicines by mouth, or who are likely to forget to take their tablets.
High-dose tablets or liquids
There are different strengths available and a dose may be taken either daily, weekly or monthly. This will depend on your situation and on which particular treatment guideline your doctor is using. Always check with your doctor that you understand the instructions – with high doses of vitamin D it is important to take the medicine correctly. The advantage of the higher-dose treatment is that the deficiency improves quickly – useful if you have troublesome symptoms.
Standard-dose tablets, powders or liquids
These need to be taken every day for about 12 months in order that the body can catch up on the missing vitamin D. This is a rather slow method of replacing vitamin D, but is suitable for prevention, or when higher doses cannot be used. A disadvantage of these medicines is that they contain either calcium or other vitamins, giving them a strong taste which some people dislike.
Maintenance therapy after deficiency has been treated
After vitamin D deficiency has been treated, the body’s stores of vitamin D have been replenished. After this, maintenance treatment is often needed long-term, to prevent further deficiency in the future. This is because it is unlikely that any risk factor for vitamin D deficiency in the first place, will have completely resolved. The dose needed for maintenance may be lower than that needed to treat the deficiency.
Cautions when taking vitamin D supplements
- If you are taking certain other medicines: digoxin or thiazide diuretics such as bendroflumethiazide. In this situation, avoid high doses of vitamin D, and digoxin will need monitoring.
- If you have other medical conditions: kidney stones, some types of kidney disease, liver disease or hormonal disease. Specialist advice may be needed.
- Vitamin D should not be taken by people who have high calcium levels or certain types of cancer.
- You may need more than the usual dose if taking certain medicines which interfere with vitamin D. These are: carbamazepine, phenytoin, primidone and barbiturates.
Are there any side-effects from treatment?
It is very unusual to get side-effects from vitamin D or calcium supplements if taken in the correct dose.
Doses of vitamin D or calcium which are too high can raise calcium levels in the blood. This would cause symptoms such as thirst, passing a lot of urine, reduced appetite, nausea or vomiting, dizziness, and headaches. If you have these symptoms you should see your GP promptly, so that your calcium level can be checked with a blood test.
Some guidelines advise that people taking high vitamin D doses should have their calcium levels checked during the first few weeks. In practice, this is not usually done unless you have symptoms of high calcium as described above.
Are there any complications of osteomalacia?
Osteomalacia causes general weakening and softening of the bones, which is improved by treatment. However, until treated, the bones are more prone to fractures (breaks). Severe osteomalacia can cause small fractures in more than one place at a time – for example, in the pelvis, thigh or ribs. Prolonged osteomalacia or osteomalacia treated very late, can cause permanent bone deformities such as kyphosis (bending of the spine) or curving of the long bones in the arms and legs.
Osteomalacia sometimes causes low levels of calcium in the blood. Theoretically, low calcium can lead to muscle spasms (cramps) or seizures – but in practice this is unlikely to happen.
Prognosis (outlook) for osteomalacia?
If treated, the outlook is very good. Most people with osteomalacia recover with vitamin D treatment. However, it can take time (months) for bones to recover and symptoms such as pain to get better or improve.
Unfortunately, if osteomalacia is undiagnosed and untreated for years, bone deformities can be permanent and cause mobility problems, pain and abnormal appearance.
With prolonged or untreated osteomalacia, the risk of getting osteoporosis (bone thinning and fractures in old age) may be increased. It is also possible that the risk of getting other diseases might be increased. This is because vitamin D is thought to help prevent some conditions such as diabetes, heart disease and cancer.
How can osteomalacia be prevented?
Various groups of people are prone to develop vitamin D deficiency. Therefore, the following groups of people are advised to take vitamin D supplements routinely.
- All pregnant and breast-feeding women.
- Breast-fed babies. (Bottle-fed babies do not need vitamin D supplements as formula milk is fortified with vitamin D.)
- Young children up to the age of five years.
- All older people aged 65 and over.
- People whose skin is not exposed to much sun. For example, people who cover their skin for cultural reasons, people who are housebound, etc.
- People who have darker skin. (For a given amount of sun exposure, people with darker skin produce less vitamin D than people with lighter skin.)
A doctor may also advise routine vitamin D supplements for people with certain gut, kidney or liver diseases, and people prescribed certain medicines.
The dose advised varies depending on your circumstances, age, etc. Your doctor, nurse or midwife will advise on the dose.
Note: pregnant women can get free prescriptions and vitamins.
Lifestyle changes to prevent osteomalacia
Vitamin D deficiency and osteomalacia can also be prevented by lifestyle changes. This involves getting more sun exposure outside, and improving the diet to include the few foods that are rich in vitamin D. (See separate article called ‘Vitamin D deficiency’ for more information.)
If you have been treated for osteomalacia
After osteomalacia has been treated, prevention will be needed so that it does not recur in the future. Most people diagnosed with osteomalacia will need to take vitamin D supplements long-term.
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- Drug and Therapeutics Bulletin, April 2006 44: 25-29. Primary vitamin D deficiency in adults. (Requires a subscription)
- Holick MF; Vitamin D deficiency. N Engl J Med. 2007 Jul 19;357(3):266-81.
- Dobson, R; Many young south Asian women in UK lack vitamin D: reporting recent research. British Medical Journal 2007;334:389 (24 February)
- Osteomalacia, Wheeless’ Textbook of Orthopaedics
- Update on Vitamin D, Scientific Advisory Committee on Nutrition, February 2007