7 Conditions Similar to Ankylosing Spondylitis

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Many people with ankylosing spondylitis (AS) receive a delayed or inaccurate diagnosis before discovering they are living with the condition. Chronic back pain and certain types of arthritis have similar symptoms to ankylosing spondylitis, making it difficult to diagnose.

Learn more about ankylosing spondylitis and similar conditions.

healthcare provider treating patient with back pain

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Why Is Ankylosing Spondylitis Difficult to Diagnose?

Ankylosing spondylitis can be challenging to diagnose for two primary reasons:

  • There is no specific test for ankylosing spondylitis.
  • The symptoms can slowly increase and worsen over time.

Even though there is no single test for ankylosing spondylitis, testing such as magnetic resonance imaging (MRI) can help to detect the condition.

Another reason ankylosing spondylitis can be challenging to diagnose is because symptoms are similar to other conditions, such as rheumatoid arthritis. However, there are differences. For example, ankylosing spondylitis generally affects the back, while rheumatoid arthritis generally affects joints such as knees, wrists, and hands on both sides of the body.

More women than men with ankylosing spondylitis are misdiagnosed despite similarities in the average age of disease onset and the time frame to seeking treatment.

Similar Diseases to AS

Ankylosing spondylitis is a type of arthritis and is in the spondyloarthritis family.

Other types of spondyloarthritis are:

The symptoms of ankylosing spondylitis include pain and back stiffness, challenges with posture, and fatigue, which mimic conditions with similar symptoms, including:

Back Pain and Injury

Injuries, diseases of the spine, and other medical conditions such as kidney stones or infections cause back pain.

Back injury such as back strain or sprain can lead to symptoms such as:

  • Back pain
  • Difficulty maintaining good posture
  • Stiffness

People with ankylosing spondylitis have a higher risk of back and spinal injuries since ankylosing spondylitis can cause bones to become brittle and fused, decrease mobility, and lead to falls. Diagnosing ankylosing spondylitis is challenging if an injury seemingly causes all the symptoms.

Fibromyalgia

Fibromyalgia is a long-term medical condition common among people with ankylosing spondylitis. Much like ankylosing spondylitis, symptoms of fibromyalgia include pain and fatigue.

Additionally, many people with ankylosing spondylitis, particularly women, are misdiagnosed with fibromyalgia. One study of people with ankylosing spondylitis found that 20.7% of women received an inaccurate fibromyalgia diagnosis compared to 6.6% of men.

Psoriatic Arthritis

Like ankylosing spondylitis, psoriatic arthritis is a type of arthritis. Symptoms of psoriatic arthritis include swelling and pain in the joints (more often in fingers and toes than in the back) and usually involves a rash.

While these symptoms differ from those commonly seen with ankylosing spondylitis, psoriatic arthritis can lead to back pain and stiffness and can be confused with ankylosing spondylitis.

Rheumatoid Arthritis

As with all autoimmune diseases, rheumatoid arthritis occurs when the immune system attacks healthy cells by mistake. Symptoms include:

  • Pain
  • Swelling
  • Stiffness
  • Fatigue

The overlap between the symptoms of both conditions leads people with ankylosing spondylitis to be misdiagnosed with rheumatoid arthritis.

Diffuse Idiopathic Skeletal Hyperostosis

Diffuse idiopathic skeletal hyperostosis is arthritis that affects tendons and ligaments in the back, leading to pain and stiffness.

While the symptoms are similar, the age of illness onset differs. Ankylosing spondylitis tends to begin in early adulthood. In contrast, diffuse idiopathic skeletal hyperostosis typically occurs later in life among people who have obesity or diabetes mellitus.

Sciatica

Sciatica is a condition caused by pressure or damage to the sciatic nerve. It begins in the lower back and causes pain and weakness in the leg. It is also linked to poor posture. Unlike ankylosing spondylitis, sciatica usually doesn't require treatment beyond rest and often goes away independently.

How to Diagnose Ankylosing Spondylitis

There is no specific test to screen for or diagnose ankylosing spondylitis. Early ankylosing spondylitis diagnosis can be challenging because spinal damage cannot always be seen on imaging tests.

Ankylosing spondylitis is diagnosed by assessing health history, getting a physical exam by a medical professional, and testing that may include:

Summary

Symptoms of ankylosing spondylitis overlap with those of other medical conditions, making diagnosis challenging. Additionally, the disease can progress slowly, and no specific diagnostic tests make misdiagnosis common. If you are experiencing symptoms of ankylosing spondylitis, contact your healthcare provider to help with diagnosis and treatment options.

A Word From Verywell

Living with pain from ankylosing spondylitis is challenging, especially when you experience delays in diagnosis and treatment. Support is available if you or someone you know is experiencing symptoms of ankylosing spondylitis.

Once you receive an accurate diagnosis, your ankylosing spondylitis can be treated. Reach out to a healthcare provider such as a primary care practitioner or rheumatologist for support.

Frequently Asked Questions

  • What’s the difference between ankylosing spondylitis and spondyloarthritis?

    Ankylosing spondylitis is a type of spondyloarthritis that affects the back. Other types affect different parts of the body or have other differences. For example, peripheral spondyloarthritis affects arms and legs, and enteropathic spondylitis affects the digestive system.

  • How often is ankylosing spondylitis misdiagnosed?

    Over one-third of people with ankylosing spondylitis are misdiagnosed. Women with ankylosing spondylitis are more likely than men to be misdiagnosed.

  • Can a blood test help confirm ankylosing spondylitis?

    While there is no test specifically for this condition, a blood test can help to confirm ankylosing spondylitis. Blood tests can check for inflammation or genes linked to ankylosing spondylitis.

21 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  12. National Institute of Arthritis and Musculoskeletal and Skin Diseases. Fibromyalgia.

  13. Johns Hopkins Medicine. Psoriatic arthritis.

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  17. Columbia University Irving Medical Center. Diffuse idiopathic skeletal hyperostosis (DISH).

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By Ashley Olivine, Ph.D., MPH
Dr. Ashley Olivine is a health psychologist and public health professional with over a decade of experience serving clients in the clinical setting and private practice. She has also researched a wide variety psychology and public health topics such as the management of health risk factors, chronic illness, maternal and child wellbeing, and child development.