Complications and Comorbidities

Reviewed by: HU Medical Review Board | Last reviewed: February 2019 | Last updated: November 2022

Ankylosing spondylitis (AS) increases the risk of certain other conditions. When people have another condition at the same time, it is referred to as a comorbidity. In some cases, people with AS may also develop complications from their disease. Some of these complications are referred to as extra-articular (beyond the joints) issues.

Common complications and comorbidities that occur in people with AS are described below. While not everyone with AS has complications or comorbidities, it is important for people with AS to regularly visit their doctor, at least each year. Many of the complications and comorbidities can be effectively treated. Finding these issues earlier can reduce the risk of permanent damage.1

Complications and comorbities of AS

Limited mobility

Because AS causes chronic inflammation in the joints and the places where tendons and ligaments attach to the joints, joint damage can occur and lead to limited mobility. There is wide variation between different people with AS, and not everyone has the same affected joints. The challenges in mobility differ based on the joints that are affected by AS. Effective treatment for AS, may include a combination of approaches, including medication, physical therapy, and exercises. These can all reduce pain and stiffness, maintain mobility, and help people engage in their daily activities.2,3

Spinal fracture, kyphosis, or stenosis

AS most often affects the spine and can lead to complications such as4-6:

  • Spinal fractures, cracks or breaks in the vertebrae
  • Kyphosis, an outward curvature of the spine which causes a hunched or rounded back
  • Stenosis, a narrowing of the spinal column that can cause pain or nerve damage


Osteoporosis is a condition in which the bones are weakened and brittle and at an increased risk of fracture. AS puts at person at greater risk of developing osteoporosis. One study found that 21% of people with AS over the age of 50 in their research study met the criteria for osteoporosis, and another 44% had osteopenia - a condition where there is bone loss but not to the degree of osteoporosis. Osteopenia may develop into osteoporosis, and people with osteopenia are at an increased risk of osteoporosis.7,8

Heart problems

While the inflammation caused by AS is primarily focused on the joints, particularly the joints in the spine, chronic inflammation occurs throughout the body. This can have damaging effects on different organs, including the heart. Chronic inflammation can affect the aorta (a large artery in the heart), causing blockages or damaging the heart. Long-term inflammation can also disrupt the heart's electrical system, causing changes in its rhythm.1

Cauda equina syndrome

A rare but potentially serious complication that can occur in people with AS is cauda equina syndrome (CES). CES occurs when nerves at the bottom of the spine become compressed. These nerves send and receive messages from the organs in the pelvis and the legs, and when they are compressed, it can lead to motor and sensory problems for the legs, bladder, and bowel control.9,10

Lung complications

There are two ways AS can cause complications for the lungs and breathing: by affecting the joints in the chest or by the systemic inflammation in the body. Lung complications from AS may include11,12:

  • Fibrosis or interstitial lung disease, a scarring of the connective tissue between the air sacs in the lung and causes shortness of breath
  • Sleep apnea, a potentially serious condition in which breathing stops and starts during sleep
  • Restriction of the chest wall due to fused joints in the ribcage
  • Spontaneous pneumothorax, a collapse of the lung that causes pain and shortness of breath
  • Lung infections

Inflammatory bowel disease

People with AS have an increased risk of developing inflammatory bowel disease (IBD), including ulcerative colitis and Crohn's disease. It is estimated that between 5% and 10% of people with AS have IBD.13 IBD can cause abdominal pain, persistent diarrhea, blood in the stool, unexpected weight loss, reduced appetite, and fatigue, and the digestive tract can become damaged, requiring surgery to remove sections.14,15

Eye problems

Between 30-40% of people with AS will experience uveitis at some time during the course of their condition. Uveitis is inflammation in the eye that occurs in the uvea (the middle layer of the eye). Uveitis can cause redness, pain, sensitivity to light, blurry vision, and excessive tears. Treatment for uveitis is important to maintain vision.16,17


Plaque psoriasis is a chronic condition causing raised, red, scaly patches on the skin. The plaques may be itchy, painful, and can crack and bleed. Psoriasis is not infectious and is a chronic condition that can go through periods of flares and remission. It's estimated that 9% of people with AS have psoriasis.18,19

Hearing loss

Hearing loss is common among people with AS. There are two types of hearing loss, conductive and sensorineural. In addition, some people have a combination of these two, which can be called mixed hearing loss. In conductive hearing loss, there are problems with the ear canal, ear drum, or middle ear (where the ear bones - the malleus, incus, and stapes - are located). Sensorineural hearing loss is caused by nerve problems in the inner ear. While people with AS can have either or both types, conductive hearing loss is more common.20,21

Oral health problems

About 15% of people with AS experience jaw involvement, where the joints of the jaw become stiff and make it difficult to open the mouth.5 In addition, people with AS are at an increased risk of developing gum disease.22


Fibromyalgia is a neurological condition that causes widespread in the body. People with AS have a greater risk of developing fibromyalgia, which can complicate their symptoms and the progression of their AS.23,24


People with AS have an increased risk of developing cancer, including cancers of the digestive tract, blood cancers, and prostate cancer.25,26 Researchers believe that the higher levels of chronic inflammation in the body that occur in conditions like AS create circumstances that may trigger cancer to grow.27 In addition, some medications (like biologics) used to treat AS may increase the risk of certain cancers.28

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