Osteomalacia

What Is It, Causes, Symptoms, and More

Author: Ashley Mauldin, MSN, APRN, FNP-BC

Editors: Ahaana Singh, Lisa Miklush, PhD, RN, CNS

Illustrator: Aileen Lin


What is osteomalacia?

Osteomalacia refers to a bone condition that causes softening or weakening of the bones due to a decreased ability to mineralize, or harden. Bones are made up of various minerals, including calcium and phosphorus, that help provide structure and integrity. An imbalance of these minerals can interfere with bone health and can cause an individual to develop osteomalacia. Osteomalacia is most often seen in adults. It is not to be confused with rickets, a bone disease seen in children, that includes impaired mineralization at the growth plate and softening or weakening of the bones.

What causes osteomalacia?

The most common cause of osteomalacia is a vitamin D deficiency, typically resulting from an inability to form or absorb vitamin D. By helping absorb calcium and phosphorus and maintaining their levels in the blood, vitamin D plays an important role in forming and maintaining bones. When there is a deficiency of vitamin D, calcium and phosphorus are not able to be absorbed or adequately maintained in the blood. This results in an insufficient amount of minerals available for bone formation, ultimately causing softened or weakened bones. 

Vitamin D is produced in the skin by way of sunlight, and if there is a lack of sun exposure, it is unable to form. Vitamin D can also be absorbed through diet. A vitamin D deficiency can result from a diet low in vitamin D, or in cases of malabsorptive conditions; for instance, Crohn’s disease, celiac disease, or if an individual has undergone gastric bypass surgery. Additionally, long term use of certain seizure treatment medications, such as phenytoin or phenobarbital, can interfere with the body’s ability to absorb vitamin D

Osteomalacia can also develop in cases of kidney disease or kidney failure. The kidneys play a key role in filtering phosphorus out of the blood. When the kidneys are impaired, it can result in a buildup of phosphorus. The kidneys also activate vitamin D into its active form (known as calcitriol), which ultimately maintains the balance of calcium and phosphorus in the blood. With loss of kidney function, increases in phosphorus levels and decreases in active vitamin D stimulate increased production of the parathyroid hormone, resulting in hyperparathyroidism. Elevated parathyroid hormone levels will work to balance the phosphorus in the blood by stimulating the release of calcium from the bones. As calcium leaves the bones, they can become brittle and weak.

Liver disease can also result in osteomalacia due to changes in the way vitamin D and calcium are metabolized. This can cause impaired bone formation, mineralization, and reabsorption, as well as a decrease in the amount of calcium absorbed from the intestines. 

Additional risk factors for developing osteomalacia include being biologically female and having a darker skin pigmentation. Older adults are also more prone to developing osteomalacia due to decreased vitamin D levels with age.

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What are the symptoms of osteomalacia?

Symptoms of osteomalacia vary depending on stage. Early stage osteomalacia can often show no apparent symptoms. As it progresses, however, individuals may develop bone pain in the lower back, pelvis, and hips. People often also experience muscle spasms and muscle weakness. For some, osteomalacia can cause muscular and bone pain all over the body.

Over time, the development of fragile bones increases the risk of fractures and trauma. If an individual with osteomalacia experiences any falls, they are more likely to have multiple fractures due to the weakened bone structure.

How is osteomalacia diagnosed?

Osteomalacia is first assessed through a review of medical history and a physical exam which can reveal a history of past fractures, recurrent bone pain, or difficulty walking. Subsequent blood tests can then show any decreases in vitamin D, calcium, or phosphorus levels. If the osteomalacia is secondary to kidney failure or hyperparathyroidism, blood tests will also show an increase in parathyroid hormone levels. X-rays may also be performed to look at decreased bone mineral density. An individual with osteomalacia may also show “Looser lines”, or pseudofractures, which are transverse lucencies that look like fractures. The transverse lucencies will appear slightly darker than other areas on an X-ray.

If—with all other diagnostic tests performed—osteomalacia is suspected but unconfirmed, a bone biopsy can also be conducted. In most cases, however, a biopsy will not be required for diagnosis. 

How is osteomalacia treated?

Osteomalacia treatment primarily focuses on replenishing deficient vitamins and minerals. In most cases, increased dietary intake of vitamin D is required, either through supplements, diet, or both. An increase in calcium or phosphate intake may also be recommended. 

In cases secondary to kidney failure, treatment involves normalizing the levels of the parathyroid hormone. This is usually accomplished through dietary changes to reduce the amount of phosphorus consumed. Medications, such as Rocaltrol and Calcijex (synthetic calcitriol) or Sensipar (calcium reducer) may also be recommended. Sensipar is often used in combination with dialysis for individuals with severe kidney failure

How do you prevent osteomalacia?

Osteomalacia can often be prevented by getting enough vitamin D. A diet rich in nutrients and minerals, such as vitamin D and calcium, is highly recommended. In addition, it is often recommended to maintain a healthy body weight, get safe exposure to sunlight, and follow up regularly with a healthcare provider. In individuals with increased risk factors for vitamin D deficiency and subsequent osteomalacia, vitamin D and calcium supplements may be recommended.

What are the most important facts to know about osteomalacia?

Osteomalacia and rickets are bone diseases that cause a softening or weakening of the bones. Osteomalacia is mainly present in adults, while rickets refers to the impaired mineralization at growth plates and softening or weakening of the bones in children. The most common cause of osteomalacia is vitamin D deficiency, either from an inability to produce it, or an inability to properly absorb it. Osteomalacia can also develop as a result of kidney failure or elevated parathyroid hormone levels. Diagnosis and treatment of osteomalacia is aimed at identifying the cause and correcting the underlying nutrient deficiencies. A medical history review and physical examination may reveal any bone pain and history of fractures with falls. Blood tests can confirm decreased vitamin D, calcium, and phosphorus levels. In some cases, imaging (X-rays) or a bone biopsy may be required for further confirmation. Treating osteomalacia, in most cases, focuses on dietary changes or the use of oral vitamin D and calcium supplements. For those with kidney failure, specific medications may be required to balance mineral and hormone levels. In order to prevent osteomalacia, it is highly recommended to eat a vitamin D-rich diet.

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Related links

Bone Remodeling and repair
Osteomalacia
Rickets
Skeletal system

Resources for research and reference

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