Osteomalacia

Updated on May 18, 2022 at 1:24 PM UTC

What is osteomalacia?

Osteomalacia is the softening of bones in the body, leading to bone pain, bone tenderness, bending of the long bones and, in some cases, fractures.

Although bone appears to be hard, it is mostly made of collagen, the same material that flexible body parts like skin and tendons are made from. Bones become hard when a mineral, calcium phosphate, coats the collagen fibres in a process called mineralization. The more mineral in the bone, the harder the bone is. 1

New bone is being formed in the body all the time. If the new collagen fibres are not properly coated with mineral, the bones become soft and may bend and break. This condition is known as osteomalacia. 2

The most common cause of osteomalacia is a lack of vitamin D. In the United States, incidences of osteomalacia are rare, depending on location. People who live in cooler climates, particularly people with darker skin, are more at risk of developing osteomalacia.

In most cases, the prognosis is good, and the condition can be cured with straightforward treatment, often involving a course of vitamin and/or mineral supplements.

If you think that you might have a health condition, try using the Ada app to find out more about your symptoms.

Symptoms of osteomalacia

Soft bones are a typical sign of osteomalacia. It can lead to symptoms such as: 3 4 5

Pain or tenderness in the bones
Muscle spasms and/or cramps
Muscle weakness, particularly in the thighs and buttocks
Waddling gait and/or difficulty walking
Feeling of pins and needles, known as paresthesia, or numbness around the mouth or in the arms and legs, in cases of calcium deficiency

Very severe cases of osteomalacia may result in:

Bone deformity, i.e. bending of the long bones
Pseudofractures, known as Looser’s zones, particularly in bones that bear weight such as the feet and pelvis
Fractures of bones, especially after an event that would not usually cause such severe consequences, e.g., a non-severe fall in a middle-aged person

Osteomalacia is sometimes confused with other conditions which involve signs of weakening of bones, specifically rickets, osteoporosis and osteopenia. See the resources on rickets and osteoporosis for more information.

If you think that you might have a health condition, try using the Ada app to find out more about your symptoms.

Causes

Osteomalacia is typically caused by a deficiency of vitamin D and/or phosphorus. Although vitamin D deficiency is increasing in some countries, this does not always lead to osteomalacia. 6

There are rare forms of osteomalacia that are caused by genetic factors or underlying disorders that affect the body’s ability to absorb vitamin D or phosphorus, such as liver disease, kidney failure or celiac disease, an autoimmune disorder that can damage the intestinal lining, stopping it from metabolising nutrients well. 2

Lack of calcium can also cause osteomalacia, but, in Western countries, it’s rare for people to have a calcium deficiency. 2

Vitamin D deficiency and osteomalacia

Vitamin D is important for healthy bones because it encourages the body to absorb calcium and phosphorus. 7 The body makes vitamin D when ultraviolet (UVB) waves, which are found in sunlight, directly touch the skin, interacting with the body’s chemistry to form vitamin D3. 8

People who live in climates with seasons lacking strong sunshine, such as autumn and fall in the northern hemisphere, or who are unable to get direct sunlight on their skin, will not produce enough vitamin D to create the minerals which harden bones. 9 This increases a person’s risk of developing osteomalacia.

Vitamin D deficiency has also been linked to breast cancer, bowel cancer, prostate cancer, obesity, heart disease and type 2 diabetes.

Phosphate deficiency

Less common forms of osteomalacia are caused by conditions that affect the body’s ability to absorb phosphates. These include: 10

Rare genetic disorders
Kidney disease, though more common in advanced stages, and kidney failure
Liver disease

Certain drugs

Some medications can increase the risk of osteomalacia when taken for a long time and/or in higher dosages.

Some older epilepsy medications linked to osteomalacia include: 11

Sodium valproate
Carbamazepine
Phenobarbital
Topiramate
Phenytoin

Other medications that are associated with osteomalacia include: 12

Cholestyramine, used to reduce cholesterol
Rifampicin, an antibiotic
Isoniazid, used for treating tuberculosis
Antacids containing aluminum
Saccharated ferric oxide, used to treat anemia
Biphosphonates, used to treat osteoporosis and bone metastases
Fluoride, used to prevent tooth decay

Risk factors

People who live in cooler climates, where there isn’t much sunlight during the autumn or fall, are at risk of developing osteomalacia. 2

Anyone who covers most of their skin when they go outside, uses very strong sunscreen or can’t get outside due to illness or disability, is unlikely to be able to make enough vitamin D from sun exposure, even in spring or early summer. 5

People with dark skin, who live in countries without strong sunlight, are particularly at risk. This is because darker skin does not make as much vitamin D as lighter skin. 9

Lactose-intolerant people may not get enough calcium and vitamin D in their diets to produce strong bones, and so may need to consume other foods high in calcium and vitamin D instead. 5

Osteomalacia diagnosis

Osteomalacia diagnosis can be carried out with a blood test measuring levels of calcium, vitamin D and phosphate in the body. 2 If low levels of these are found, then a person may be diagnosed with osteomalacia or another bone disorder.

X-rays, CT and MRI scans can detect bone fractures.

Rarely, a bone biopsy, also known as a closed or needle biopsy, may be done, in which a small sample of bone is removed and examined under a microscope.

If you think that you might have a health condition, try using the Ada app to find out more about your symptoms.

Treatment and Prevention

Osteomalacia is treatable, usually with vitamin and/or mineral supplements, and most people can be cured. It is generally treated by administration of vitamin D, calcium and, if needed, also phosphorus. 5

If the osteomalacia is caused by an underlying condition, this will also need to be treated. Osteomalacia caused by phosphate deficiency is usually due to another condition. Treatment will be recommended by a doctor. 4

Bone will begin to strengthen within a few weeks to a few months and should be fully healed within six months. However, pain and muscle weakness may continue to be experienced during the healing process. 5 13 2

Vitamin and mineral supplements

The amount of supplementary vitamin D a person may require depends on factors such as their age, how much natural sunlight they receive where they live and any possible other influencing factors, like having certain medical conditions or taking certain drugs that influence how the body takes up, processes or builds vitamin D.

For people living in the United States, the National Academies of Science, Engineering and Medicine recommends the following daily intakes for adults: 14

Vitamin D: 600 IU (international units) / 15 mcg a day
Calcium: 1,000 mg a day
Phosphorus: 700 mg a day

Sources of vitamin D in food

Another way of getting vitamin D is through diet, though it does not occur in many foodstuffs. Vitamin D is found in foods such as:

Oily/fatty fish
Liver
Egg yolks
Cheese
Foods fortified during the manufacturing process

Maintaining healthy bones

There are many things people can do in day-to-day life to promote healthy bones for osteomalacia prevention. These include: 2

Having a diet rich in vitamin D
Getting a healthy amount of sun exposure
Reducing alcohol intake
Stopping smoking
Exercising regularly
Maintaining a healthy weight

Other medications that are associated with osteomalacia include: 12

Cholestyramine, used to reduce cholesterol
Rifampicin, an antibiotic
Isoniazid, used for treating tuberculosis
Antacids containing aluminum
Saccharated ferric oxide, used to treat anemia
Biphosphonates, used to treat osteoporosis and bone metastases
Fluoride, used to prevent tooth decay

FAQs

Q: Which population group is at highest risk for osteomalacia?
A: The population group most at risk of osteomalacia varies in different parts of the world. In high-latitude countries, the most-at-risk groups are dark-skinned populations. In parts of the world which receive large amounts of sunlight, such as the Middle East, Africa and the Indian subcontinent, predominant causes of osteomalacia include traditional diets low in calcium, dark skin and cultural, full-body clothing. 16

Q: Osteomalacia vs osteoporosis - what is the difference?
A: Osteomalacia is the softening of bones, usually due to a lack of vitamin D. Osteoporosis is when bones lose density and become brittle, usually because of age or hormone related changes. While the signs and symptoms of osteoporosis and osteomalacia may be similar, the underlying causes and treatments are different.