Osteomalacia

Published by Bupa's Health Information Team, November 2010.

This factsheet is for people who have osteomalacia, or who would like information about it.

Osteomalacia is a condition that affects the bones, making them soft and weak, and more likely to fracture. It's usually caused by a deficiency in vitamin D. In the UK, it commonly affects people of Asian, African–Caribbean or Middle Eastern origin or those aged 65 and over.

About osteomalacia

Bone development

Healthy bone consists of a strong mesh made of protein and minerals (particularly calcium). Throughout your lifetime, your bones continuously maintain and repair themselves. This is done through a process called ‘bone turnover’, during which tiny areas of old bone are removed and replaced with new bone.

The strength of your bones depends on the amount of minerals laid down in the hard outer shell. This is done through a process called mineralisation. Minerals such as calcium and phosphorus are absorbed from the food you eat and deposited in your bones. You also need vitamin D for this process because it helps your body to absorb calcium and makes sure it gets to where it's needed (eg your bones or teeth).

During childhood, mineralisation helps your bones to grow and develop, whereas in adulthood it maintains and repairs them.

Osteomalacia

Osteomalacia develops when your bones don't get enough of the minerals they need. This makes them soft and weak, and can cause them to crack or break more easily. This can cause deformities.

Osteomalacia only affects adults. A similar condition that affects children’s bones is called rickets.

Symptoms of osteomalacia

The symptoms of osteomalacia can be quite vague – you may just feel generally unwell. However, specific things to look out for include:

• bone pain, especially in your hips and legs
• backache
• muscle weakness, especially at the front of your thighs and in your buttocks – this may make you rock from side to side when you walk, or you may find it difficult to get up from a chair or squatting position

Osteomalacia can sometimes be caused by other conditions, such as kidney or liver disease. Often, it's the symptoms of these other conditions that are picked up first and later lead to a diagnosis of osteomalacia.

Complications of osteomalacia

If you have osteomalacia, you may be more at risk of fractures. Stress fractures are tiny cracks in the bone. These can often be the cause of bone pain and can lead to complete fractures

If you have very low levels of calcium in your blood, you may develop hypocalcaemia. If this is left untreated, it can affect your brain and cause confusion, memory loss, depression or hallucinations. The symptoms of extreme hypocalcaemia include:

• muscle aches
• tingling in your hands and feet
• muscle twitches
• difficulty breathing (this is caused by spasms of the muscles in your throat)
• an abnormal heart rhythm

If you have any of these symptoms, see your GP.

Causes of osteomalacia

Vitamin D deficiency

Vitamin D is important for bone health. Osteomalacia is usually caused by a prolonged lack of vitamin D. Vitamin D is produced naturally by your body when your skin is exposed to sunlight and can also be obtained from some foods, such as oily fish.

In the UK, nearly half of all adults have a vitamin D level lower than is thought necessary to protect against osteomalacia during winter and spring.

You’re more at risk of developing vitamin D deficiency that may lead to osteomalacia if you:

• are of Asian, African-Caribbean or Middle Eastern descent and living nearer the North or South Poles – the darker your skin, the less likely you are to get enough vitamin D from the milder climate
• cover up extensively with clothing (for example, by wearing a burka)
• don't spend much time outside
• use too much sunscreen
• are aged 65 years and over
• have a poor diet (lacking in vitamins and nutrients) or eat a restrictive diet (eg if you’re vegetarian or vegan)

Less commonly, vitamin D deficiency can be caused by underlying conditions, such as:

• malabsorption – this is when your body can’t properly absorb certain nutrients; it can happen if you have a condition such as coeliac disease or chronic pancreatitis, or it can be caused by some stomach surgery procedures
• liver disease
• kidney disease
• metabolic disorders – this is when your body can’t make energy properly from the food you eat, causing you to have too much or too little of substances that keep you healthy

Vitamin D deficiency can also be a side-effect of some anti-epileptic medicines, such as carbamazepine, phenytoin and sodium valproate.

Phosphate deficiency

Occasionally, osteomalacia can be caused by a lack of phosphate in your body. This stops your bones mineralising properly. Having too little phosphate in your body can be caused by taking certain antacid tablets (such as aluminium hydroxide) over a long period of time, kidney disease or a rare inherited disease called hypophosphataemic rickets.

Mineralisation defects

This is when the cells that lay down the minerals in your bones during the mineralisation process don't work properly.

Diagnosis of osteomalacia

Your GP will ask about your symptoms and examine you. He or she may also ask you about your medical history.

If your GP thinks you have osteomalacia, he or she will ask you to have a blood test. This will measure the levels of vitamin D, calcium and phosphate in your blood. You may also be referred to the hospital for an X-ray to check for stress fractures, especially if any parts of your body are painful or tender.

You may be referred to a specialist for treatment or monitoring if there is no obvious cause for your osteomalacia or you don't respond to the treatment prescribed by your GP. If you have an underlying condition that needs further treatment, your GP may refer you to a specialist.

Your GP may refer you to a doctor who specialises in metabolic bone disease if your osteomalacia is caused by phosphate deficiency, a problem with mineralisation of your bones, or another underlying condition.

Treatment for osteomalacia

Osteomalacia is often caused by a lack of vitamin D, so your GP will usually prescribe you daily vitamin D and calcium supplements. If your osteomalacia is severe or you have problems remembering to take your tablets, he or she may recommend that you have vitamin D injections. You will have these once a month for the first three months and then every six or 12 months depending on how much vitamin D you need.

Taking vitamin D supplements and calcium is effective for treating osteomalacia. However, you may still have bone pain and muscle weakness for several months after you start your treatment.

You may need to continue taking vitamin D supplements for the rest of your life, depending on your lifestyle and where you live.

It's important that you don’t take more than the dose of vitamin D supplement that your GP recommends. If you have too much vitamin D, you may develop vitamin D toxicity and hypercalcaemia, which is an excess of calcium in your body. If you have hypercalcaemia, you may lose your appetite and feel sick or vomit. This can lead to you feeling weak, nervous and excessively thirsty. If left untreated, hypercalcaemia can damage your kidneys.

Always read the patient information leaflet that comes with your supplements and if you are pregnant or breastfeeding, ask your pharmacist or GP for advice first. Talk to your GP before taking vitamin D supplements if you are taking diuretics for high blood pressure or have a history of kidney stones or kidney failure.

Prevention of osteomalacia

There are several things you can do to reduce your risk of osteomalacia.

Diet

Make sure that you eat foods that are rich in calcium and vitamin D. Good sources of calcium include:

• dairy products (for example, milk, yoghurt and cheese)
• bread made with fortified flour
• soya beans and tofu
• leafy green vegetables (for example, broccoli and cabbage but not spinach)
• fish that includes the bones (for example, sardines and pilchards)

Diet alone isn't usually enough to give you your daily requirement of vitamin D. However, you can get some vitamin D from:

• oily fish (for example, sardines, mackerel and fresh tuna)
• eggs
• breakfast cereals that are fortified with vitamin D

Sun

You may get enough vitamin D during summer by spending frequent short spells in the sun without wearing sunscreen (the exact time you need is different for everyone, but is typically only a few minutes in the middle of the day). However, do not let your skin redden.

Supplements

If you don't get much sun exposure and particularly during winter months, taking up to 25 micrograms of vitamin D (two high-strength 12.5 microgram capsules) can help to make sure you get enough.

Always read the patient information leaflet that comes with your supplements and if you are pregnant or breastfeeding, ask your pharmacist or GP for advice first. Talk to your GP before taking vitamin D supplements if you are taking diuretics for high blood pressure or have a history of kidney stones or kidney failure.

For answers to frequently asked questions on this topic, see Common questions.

For sources and links to further information, see Resources.