Diffuse idiopathic skeletal hyperostosis (DISH) and ankylosing spondylitis (AS) are both types of arthritis. DISH causes ligaments to harden and bone spurs to form. AS causes inflammation in the vertebrae of the spine.

DISH and AS can both cause stiffness and pain. DISH can affect the upper back and neck, while AS may cause symptoms in the lower back and hips. Treatment can help manage both conditions and prevent them from progressing.

In this article, we compare the cause, symptoms, diagnosis, treatment, and outlook of DISH and AS.

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DISH, which specialists also term Forestier disease, is a form of arthritis. DISH usually affects the tendons and ligaments around the spine, but it can also affect tendons and ligaments in other areas of the body.

DISH causes the ligaments to become calcified, which means they harden. DISH also leads to abnormal new bone growth called bone spurs. These bone spurs usually form where ligaments and tendons connect to bones.

DISH may cause hardening of bones throughout the body and may cause bone spurs in the:

  • hips
  • knees
  • shoulders
  • ribs
  • feet
  • hands

AS is a form of arthritis that causes inflammation in the vertebrae of the spine, which can cause stiffness.

In some severe cases, AS can cause the bones in the spine to fuse together, creating a rigid spine that is less mobile.

AS can also lead to inflammation in other joints of the body and affect the:

  • shoulders
  • ribs
  • hips
  • knees
  • ankles
  • hands
  • feet

The following table provides a comparison of DISH and AS:

DISHAS
SymptomsIt may produce no symptoms in the early stages but will eventually cause pain and stiffness in the upper back and neck or in other affected parts of the body. The pain may worsen over time.

Other symptoms can include:
difficulty swallowing and breathing
• potential paralysis of the arms and legs
• increased risk of spinal fractures
sleep apnea
It can cause pain and stiffness in the lower back or hips, which may come and go or last over time. Pain may be worse after periods of inactivity.

AS can also affect other parts of the body, producing additional symptoms.
CausesThere is no known cause, but it may be due to a combination of risk factors leading to abnormal bone growth.There is no known cause, but genetics and environmental factors may play a role.
Risk factors • being male
• being over the age of 50 years
• having diabetes
• having obesity
• engaging in repetitive heavy lifting
• taking synthetic vitamin A medication
• genetics
• being male
• being under the age of 45 years
• genetics and family history of AS
• certain medical conditions
• regular gastrointestinal (GI) infections
TreatmentThere is no cure, but the following can help manage the symptoms:
physical therapy
• regular exercise
blood sugar control
• weight management
• pain relief medication
• surgery, in severe cases
There is no cure, but the following can help manage the symptoms and prevent progression:
• physical therapy
• medication to reduce pain and inflammation
• surgery, in some cases
DiagnosisX-rays
CT scans
MRI scans
• X-rays
blood tests
OutlookThe outlook is good, with no effect on life span. Treatment can help prevent DISH from worsening.Treatment can help prevent AS from progressing and help people enjoy a good quality of life.

Below, we list symptoms that AS and DISH can produce.

DISH

Individuals with DISH may not experience any symptoms, and they may only discover they have DISH through imaging tests.

Other people may have severe symptoms or symptoms that worsen over time.

If a person does have symptoms of DISH, they may experience pain and stiffness in the back.

Other symptoms can include:

  • pain and stiffness in the back, especially the upper back and neck, which may worsen over time or feel worse after waking up
  • a limited range of motion in the back
  • a hoarse voice or difficulty swallowing and speaking due to the compression of nerves in the neck
  • tingling or numbness in the legs due to compressed nerves in the lower back
  • potential paralysis of the legs or arms, if compression has occurred in the spinal cord
  • increased risk of spinal fractures or fractures in other bones that DISH affects
  • sleep apnea
  • decreased capacity in the lungs if DISH affects the ribs
  • difficulty breathing if DISH leads to airway obstruction

AS

People may have mild or severe symptoms of AS, and the symptoms may be long-lasting or come and go.

The Spondylitis Association of America (SAA) notes that the onset of symptoms can vary. Although they usually appear between the ages of 17 and 45 years, they can also begin during childhood or later on in life.

Common symptoms of AS can include pain and stiffness in the lower back and hips, which may progress to other parts of the body.

The pain can worsen after rest or periods of inactivity, such as sitting for a long time, or when sleeping. The pain may improve with movement and exercise.

AS is a systemic condition, which means that it can affect the entire body rather than just one part.

AS can affect the:

Other symptoms of AS may also include:

Learn more

In the sections below, we discuss causes of DISH and AS.

DISH

In individuals with DISH, a buildup of calcium salts in the tendons and ligaments causes bones to harden, or calcify. It can also lead to the formation of bone spurs. However, researchers are still not sure what causes the calcification.

Research suggests that the bone changes in DISH are due to abnormal growth of the cells that form bones, known as osteoblasts, in the area where tendons and ligaments connect to bone.

Causes of this abnormal bone growth may include:

  • a physical impact, such as heavy lifting or repetitive movements
  • certain dietary factors, such as long-term exposure to high vitamin A levels
  • some medications, including long-term use of synthetic vitamin A or retinoids
  • genetics, which may make it more likely to develop DISH
  • metabolic conditions, such as diabetes, obesity, and acromegaly
  • abnormalities of fat-derived hormones, such as leptin, and growth hormones

There is no one clear cause of DISH. Research suggests that a combination of the above factors may lead to abnormal bone growth.

AS

There is no known cause of AS, although certain genes may play an important role. Environmental factors, such as a bacterial infection, may also trigger AS in people who are susceptible to the condition.

Some researchers believe that if a breakdown in the defenses of the intestines happens, certain bacteria are able to pass into the bloodstream and alter the body’s immune response, triggering AS.

Certain factors can make it more likely for a person to develop DISH or AS.

DISH

According to the Arthritis Foundation, risk factors for DISH include:

  • being male
  • being over the age of 50 years
  • having diabetes or another condition that affects insulin levels, such as prediabetes or obesity
  • having taken synthetic vitamin A medication, such as isotretinoin, which is acne medication
  • being a member of the Pima tribe
  • having unusual anatomy of the spine
  • engaging in repetitive movement or lifting heavy objects, although this may or may not be a factor

One of these risk factors alone will not cause DISH, but a combination of factors may increase the risk of developing the condition.

AS

Although AS can affect anyone, certain factors may increase a person’s risk of developing AS:

  • genetics and having a family history of AS
  • being under the age of 45 years
  • being male
  • having certain conditions, such as Crohn’s disease, ulcerative colitis, or psoriasis
  • having regular GI infections

In the following sections, we describe treatment options for DISH and AS.

DISH

Although there is currently no cure for DISH, there are treatments that can help manage symptoms and lessen pain and stiffness. They may also help prevent the condition from worsening.

Treatment includes:

  • getting exercise such as swimming regularly and receiving physical therapy to manage pain, reduce stiffness, and increase range of motion
  • applying heat or a warm compress to help ease stiffness after waking up
  • maintaining weight and blood sugar within a healthy range
  • wearing orthotics, which are shoe inserts that can make walking easier and more comfortable for people with bone spurs in the feet
  • taking pain relief medication, such as acetaminophen and nonsteroidal anti-inflammatory drugs
  • receiving corticosteroid injections for severe pain and to help people return to exercise
  • in rare cases, undergoing surgery if bone spurs are obstructing the airways or compressing the spinal cord

AS

Treatment for AS can help manage symptoms, improve posture, and prevent the condition from progressing.

Treatment may include:

  • medication to reduce inflammation and relieve pain
  • physical therapy to strengthen muscles, improve flexibility, and alleviate pain
  • surgery if AS is causing severe damage to joints

Diagnosis for DISH and AS involves a physical examination and imaging tests.

DISH

Doctors may diagnose DISH by assessing pain and stiffness in the upper back and neck and a decreased range of motion and by ordering imaging tests, such as X-rays, CT scans, and MRI scans.

Imaging tests help rule out other conditions and allow doctors to see which part of the skeleton DISH is affecting.

AS

To diagnose AS, doctors may:

  • take a detailed medical history, including family history
  • carry out a physical examination
  • order X-rays
  • order blood tests for genetic markers associated with AS

DISH and AS have different outlooks.

DISH

According to the National Center for Advancing Translational Sciences, the long-term outlook for DISH is usually good, as the condition does not affect a person’s life span.

However, DISH can cause significant complications, such as:

  • chronic pain
  • loss of range of motion in affected joints
  • difficulty swallowing due to bone spurs in the neck
  • paralysis or loss of feeling due to compression of the spinal cord

A range of treatments can help manage DISH and may reduce the risk of complications.

AS

The course of AS can vary from person to person, and the outlook may depend on the severity of the condition.

According to the SAA, some people may experience infrequent pain and discomfort, while others may have longer periods of more severe pain and stiffness.

AS is a chronic condition that people will need to manage over the course of their life. Treatment can help manage symptoms and prevent the condition from progressing.

A person should contact a doctor if they have any symptoms of DISH. The doctor can perform a complete history and physical examination.

Symptoms of DISH can overlap with other conditions, and therefore individuals may require imaging tests for the doctor to determine what is causing their symptoms.

If a person has AS and only experiences mild symptoms, they should still attend regular checkups once per year to check for any complications.

DISH and AS are both types of arthritis. DISH causes ligaments to harden and bone spurs to form. DISH usually affects the spine but can also affect other parts of the body.

AS causes inflammation in the vertebrae of the spine, but it can also spread to other areas of the body. Both conditions can result in pain and stiffness.

Treatments can help manage symptoms of both conditions and prevent the arthritis from progressing.