Most people will struggle with some back pain throughout their life. It’s one of the most common conditions and a top reason people miss work. Sometimes, though, back pain may be a signal of something more serious.

You may think your back pain and spasms are the result of an injury, but it could be a rare condition called ankylosing spondylitis (AS).

Here’s what to look for to see if you should get tested.

AS is a type of arthritis that typically affects the vertebrae in your lower spine and the sacroiliac joints in the pelvis. The disease is marked by inflammation of vertebral joints and areas where ligaments, tendons, and joint capsules attach to the bone.

Repeated damage and healing cause the inflammation to progress, which can result in your vertebrae fusing together.

Other joints can also be affected, including in the following:

  • ribs
  • pelvis
  • hips
  • heels

The inflammation may also affect one or both eyes, causing pain, blurred vision, and other symptoms.

AS is an autoimmune disease, which means the body begins to attack itself in certain ways. The true cause of AS is still unknown. But some risk factors seem to play a role, including:

  • Age. Typically, those in their late teens and early to middle adulthood are affected.
  • Sex. People with a penis are more likely to have AS.
  • Heredity. The presence of a genetic marker called HLA-B27 indicates increased risk of AS.
  • Health history. Gastrointestinal or genitourinary infections also increase risk of AS.

It’s important to understand that you can develop AS even if you don’t have these risk factors. And if you have many of these risk factors, you may never develop AS.

Some people may just be genetically inclined to contract the disease. However, if you experience frequent bacterial infections in your gastrointestinal tract or genitourinary tract, these infections could trigger reactive arthritis, possibly leading to the development of AS.

The first symptoms are usually dull pain and joint stiffness in your lower back and hips, and possibly in your ribs, shoulders, and back of your heel. The pain may initially only be felt on one side.

This pain and stiffness usually improves with exercise and then worsens with rest. Symptoms may disappear for some length of time and then return. Fatigue may also be a symptom as the body deals with the inflammation.

AS symptoms can vary greatly from person to person, so your symptoms may differ.

Diagnosing AS can be difficult, as symptoms can mimic those of other disorders. Early on, problems may not even show up in tests.

It’s helpful to keep a journal of your symptoms, because your doctor will probably want to know when and where you have pain, what activities make it worse or better, and when the symptoms started.

This can help your doctor to determine the right set of diagnostic tools for you, which may include:

  • health questions, covering many of the topics listed in the previous section
  • physical exam to pinpoint “hotspots,” or areas of pain and inflammation
  • mobility testing, to see how well you’re able to bend and twist
  • blood tests, to check for the genetic marker HLA-B27 and for inflammation markers
  • X-ray or MRI scan to look for inflammation in your sacroiliac joints

The truth is, you won’t know if you have AS without a full checkup from your doctor. If you’re worried, it’s important to talk with your doctor about all of your symptoms and what they could mean.

You may be wondering if that pain in your lower back is something to be worried about. It’s time to call your doctor if you notice one or more of these symptoms:

  • You’ve begun feeling pain and stiffness in your lower back or pelvic area, especially if it’s worse in the morning or at other times of rest.
  • Exercise lessens your pain.
  • These symptoms have come on gradually, but have lasted for at least 3 months.
  • The pain wakes you up during the night and prevents you from sleeping.
  • Nonsteroidal anti-inflammatory drugs, like ibuprofen (Advil) and naproxen (Aleve), help your symptoms.
  • You notice pain in your rib cage, and it’s difficult or painful to draw a full breath.
  • One or both of your eyes are red, swollen, or painful.
  • You notice blurred vision and extreme sensitivity to light.

Even though there’s currently no cure for AS, a range of treatment options can help you feel better and continue to lead a full and active life, add prevent the disease from getting worse.

Speak with your doctor about your discomfort to get the help you need.