Lung Complications and Ankylosing Spondylitis

Written by: Emily Downward | Last reviewed: February 2019 | Last updated: November 2021

Ankylosing spondylitis (AS) is a form of chronic, inflammatory arthritis that primarily affects the spine and the locations where ligaments and tendons attach to the bones (entheses). In some people, peripheral joints in the arms and legs can also be affected. The chronic inflammation can also cause extra-articular (beyond the joint) manifestations, such as lung complications.1,2

AS and lung problems

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.

AS may affect the joints of the ribcage, such as those between the ribs and the spine or between the ribs and the breastbone. The chronic inflammation of AS wears away at the bone of the joints. As the body works to replace the lost bone, it can create excess bone, leading to a fusing of the joint. The entheses and ligaments may also become calcified, called syndesmophytes. Fused joints between the ribs and the spine or the ribs and the breastbone can limit the movement of the chest and make it difficult to fully expand the chest cavity, causing chest pain or difficulty taking deep breaths.3

While the inflammation is primarily focused on the joints, particularly the joints in the spine, chronic inflammation occurs throughout the body and can have damaging effects on the lungs, causing scarring of the lung tissue.1

Types of lung problems with AS

The chronic inflammation of AS can damage the lungs causing complications including:

  • Fibrosis or interstitial lung disease, a scarring of the connective tissue between the air sacs in the lung and causes shortness of breath1,4
  • Sleep apnea, a potentially serious condition in which breathing stops and starts during sleep1,5
  • Restriction of the chest wall due to fused joints in the ribcage1
  • Spontaneous pneumothorax, a collapse of the lung that causes pain and shortness of breath1,6
  • Lung infections2

Prevalence of lung problems with AS

Lung problems are not as common as other extra-articular manifestations of AS, such as inflammatory bowel disease, eye inflammation (uveitis), skin problems, lung and kidney problems. Estimates on how many people with AS experience lung complications from research studies have varied widely, with data ranging from 1% to 30%. Most studies have found that lung complications increase with the length of time a person has AS, and some early lung changes may not have any symptoms.1,7,8

Diagnosis

While x-rays can show changes in some people, high-resolution computed tomography (HRCT) has demonstrated to be more effective in evaluating lung complications in people with AS.1

Lung complication risk factors with AS

Other factors that increase a person's risk of developing lung problems include smoking, exposure to environmental or workplace toxins, overweight or obesity, and increasing age.4,5

Treamtment

The scar tissue of interstitial lung disease that can build up and reduce the lungs' ability to function is irreversible. Although several biologic medications are now being used to treat certain people with AS, their effects on lung issues is unclear.2

For sleep apnea, devices like continuous positive airway pressure (CPAP) or surgery may help with symptoms.5

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