An Overview of Osteomalacia

A Disease of Softened Bones

In This Article

Table of Contents

The word “osteomalacia” comes from the Greek roots “osteon” and “malakia,” meaning “bone” and “soft.” The medical condition may cause pain, muscle weakness, difficulty walking, and an increased risk of bone fracture. When caused by vitamin D deficiency, osteomalacia is sometimes called “hypovitaminosis D osteopathy. Elderly persons have a particularly high risk of osteomalacia.

Symptoms

You may not notice any symptoms from osteomalacia, especially if your condition is not severe. But some people notice problems like bone pain and muscle weakness. Sometimes these symptoms come and go, and they might be worse in the winter compared to the summer.

People with osteomalacia may have difficulty with walking, and they may have a kind of “waddling” gait. They might have difficulty rising from a chair or walking up and down stairs. Often the pain is worse when you put weight on your bones and start to walk.

In people who have very severe osteomalacia, there might be certain deformities of the skeleton. For example, they might have a very hunched back (called kyphosis).

People with osteomalacia also have an increased risk of fractures compared to someone without osteomalacia. So a fall that wouldn’t have caused a fracture in a healthy person might cause a fracture in someone who has osteomalacia.

Causes

What Is Bone Mineralization?

In order to understand what causes osteomalacia, it’s helpful to learn about the structure of your bones. Living cells in your bone secrete proteins that form osteoid, a material that forms your bone’s underlying structure. Cells then secrete hard substances containing minerals like calcium and phosphate. These are tightly networked together and connected to the underlying protein structure. This process is called mineralization. The minerals are what gives your bones their hardness and resistance.

Normally, throughout your life, there is a certain amount of bone turnover. That is, parts of your bones are being broken down, while simultaneously other parts are reforming bone tissue. In osteomalacia, some of the existing underlying bone matrix becomes unmineralized. Also, when new bone is formed, it doesn’t become properly hardened and mineralized. Another way to put it is that there is a decrease in the amount of calcium and other minerals for a given unit of underlying protein bone matrix. That makes the bones too soft.

Causes of Osteomalacia

Vitamin D is important for proper mineralization of new bone matrix. So it’s not surprising that vitamin D deficiency is a major cause of osteomalacia. Vitamin D deficiency might be caused by some of the following:

  • Very low vitamin D in the diet
  • Decreased exposure to sunlight
  • Surgical resection of part of the stomach or small intestine (e.g., for weight loss surgery)
  • Celiac disease
  • Certain medications (like anticonvulsants)
  • Hyperparathyroidism
  • Paget’s disease

Almost all people who have severe vitamin D deficiency over a long period of time will develop osteomalacia. However, not everyone who is found to have low levels of vitamin D on a blood test has osteomalacia. It usually only happens if these levels get exceptionally low.

Osteomalacia can also be caused by a deficiency in some of the minerals needed to harden bones. So deficiencies of phosphate can lead to osteomalacia. Some of the causes of hypophosphatemia include:

  • Certain genetic hereditary syndromes affecting phosphate
  • Certain rare kinds of tumors
  • Excess intake of antacids
  • Certain rare genetic kidney problems

Rarely, osteomalacia can also be caused by a side effect of certain medications used to treat osteoporosis, such as sodium fluoride and etidronate.

Osteomalacia is related to a very similar disease called rickets. Both of these diseases involve defective mineralization of your bones. However, in rickets this happens to bones that haven’t stopped growing, so it causes somewhat different symptoms, like bowed legs. Rickets is a disease of childhood and early adolescence. Osteomalacia, in contrast, occurs only in adults or in adolescents whose bones have stopped growing.

Is Osteomalacia Different From Osteoporosis?

The two conditions have important differences. Osteomalacia refers to decreased mineralization of the bone. In contrast, in osteoporosis, more bone is broken down than normal compared to the normal amount of new bone being formed, and mineralization is normal or just a little reduced. Osteomalacia leads to softened bones. Osteoporosis leads to bones that are too fragile and brittle. It is possible to have some features of osteomalacia as well as osteoporosis. Osteoporosis is the more common condition.

Diagnosis

A thorough medical history and medical exam provide the key starting point for diagnosis of osteomalacia. Your clinician must consider your symptoms and your total medical picture. This is important to help rule out other potential causes and eventually get the correct diagnosis.

But physicians often miss a diagnosis of osteomalacia, especially in the disease’s early stages. This is partly because it may cause vague symptoms that can be caused by a number of different medical conditions. For example, the symptoms of osteomalacia may be confused with diseases such as polymyalgia rheumatica, fibromyalgia, or even metastatic bone disease (cancer that has traveled to the bone from elsewhere in the body). Particularly for the latter, your clinician may need to run tests to make sure that an underlying cancer isn’t what is causing your symptoms.

Laboratory tests can provide some helpful clues. Key blood tests may include:

  • Vitamin D (often very low)
  • Alkaline phosphatase (usually high)
  • Parathyroid hormone (PTH)
  • Calcium
  • Phosphate
  • Tests of kidney function

Urinary tests, such as for calcium and phosphate, may be helpful as well.

These key tests may be enough to help diagnose osteomalacia, but sometimes further tests are needed. These might include:

  • X-rays
  • Other imaging tests (particularly if cancer needs to be ruled out)
  • DEXA tests

Rarely, a doctor might want to do a bone biopsy to help definitively diagnose osteomalacia. This is an invasive procedure that requires going under anesthesia. But it isn’t usually needed for a diagnosis.

It is especially important to distinguish osteomalacia from osteoporosis. It can be difficult to tell these apart, as they can have very similar features in terms of symptoms, lab results, and even imaging. For example, the DEXA scan used to diagnose osteoporosis is not good at telling the difference between osteoporosis and osteomalacia. It is also complicated, because a person can have both osteomalacia and osteoporosis. Often, such people are told they have osteoporosis, but the osteomalacia component is not diagnosed.

As part of your process of diagnosis, you might be told that you have hyperparathyroidism or “secondary” hyperparathyroidism. This refers to an elevation in the parathyroid hormone, which helps regulate calcium and other minerals in the body. If you have low vitamin D, this may cause your parathyroid gland to make a lot of parathyroid hormone. If you do have a vitamin D deficiency, and you treat it, this will probably bring both your vitamin D and your parathyroid hormone back into the normal range.

Treatment

Treatment for osteomalacia will depend on the underlying cause. For someone with osteomalacia due to vitamin D deficiency, vitamin D therapy provides an effective treatment. This works well for the majority of people with osteomalacia. You may need to start out with a very high dose of vitamin D in the first weeks or couple of months after you are diagnosed. You might also need to take calcium supplements.

You clinician may want you to get blood tests to see how well you are responding to vitamin D therapy. If you are responding well, you will probably be able to lower your dose. Depending on the situation, you may need to keep taking vitamin D over the long-term. This is likely to be the case if you have a medical condition or situation that chronically puts you at risk of having low vitamin D. In this case, you are likely to need life-long monitoring.

However, not all types of osteomalacia respond to vitamin D therapy. This might be obvious right away, or it might become apparent after vitamin D treatment doesn’t work for you. For example, if you have osteomalacia because of an underlying kidney problem, treatment of your kidney disease might make the most difference. Or if, for example, your osteomalacia was caused by a side effect of a drug, stopping that drug might be the most effective intervention. Your doctor will tailor your treatment to find what works for you.

A Word From Verywell

It can be concerning to learn that you or a loved one has a serious health condition like osteomalacia, something you might not be familiar with. But if you’ve been diagnosed, you may have finished the most difficult part. By learning more about the condition you can take the needed steps for treatment to ward off complications. Fortunately, most people with the condition respond very well to vitamin D therapy. Work with your clinician to get the best outcome.

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