Ankylosing spondylitis (AS) is a type of arthritis, so it’s not surprising that its main symptoms are pain and stiffness. That pain is usually centered in the lower back since the disease inflames joints in the spine.

But AS isn’t confined to the spine. It can affect other parts of the body, causing some surprising symptoms.

Here are 10 ways AS can affect your body that you might not expect.

Between 30 to 40 percent of people with AS develop an eye complication called iritis or uveitis at least once. You can tell you have iritis when the front part of one eye becomes red and inflamed. Pain, light sensitivity, and blurred vision are other common symptoms.

See an eye doctor as soon as possible if you have these symptoms. Iritis is easy to treat with steroid eye drops. If you let the condition go untreated, you could have permanent vision loss.

AS can inflame joints between your ribs and spine and in the front of your chest. The scarring and stiffening of these areas make it hard to expand your chest and lungs fully enough to get a deep breath.

The disease also causes inflammation and scarring in the lungs. Between the chest tightness and lung scarring, you may develop shortness of breath and coughing, especially when you exercise.

It can be hard to tell shortness of breath caused by AS from that of a lung problem. Talk to your doctor about what’s causing this symptom.

Areas where ligaments and tendons attach to bone also become inflamed when you have AS. This creates what are called “hot spots” in areas like the pelvis, chest, and heels.

Often, the Achilles tendon at the back of the heel and the plantar fascia at the base of the heel are affected. The pain can make it difficult to walk or stand on a hard floor.

AS is an autoimmune disease. That means your immune system is launching an attack against your own body. It releases inflammatory substances called cytokines. Too much of these chemicals circulating in your body can make you feel tired.

Inflammation from the disease can also make you feel tired. It takes a lot of energy for your body to control inflammation.

AS also causes anemia — a drop in red blood cells. These cells carry oxygen to your body’s organs and tissues. When your body doesn’t get enough oxygen, you’ll feel exhausted.

The early symptoms of AS sometimes seem more flu-like than signs of arthritis. Along with a low fever, some people lose their appetite or feel generally ill. These confusing symptoms can make the disease harder for doctors to diagnose.

About 10 percent of people with AS have inflammation of the jaw. Jaw swelling and inflammation is known as temporomandibular joint (TMJ) disorder. Pain and swelling in your jaw can make it hard to eat.

Appetite loss is one of the early symptoms of AS. It often goes along with general symptoms like fever, fatigue, and weight loss early in the disease.

Inflammation and scar tissue around the ribs can cause a tightness or pain in your chest. The pain may get worse when you cough or breathe in.

AS chest pain can feel like angina, which is when too little blood flow is getting to your heart. Because angina is an early warning sign of a heart attack, see a doctor immediately if you’re experiencing this symptom.

Rarely, scars can form on the nerves at the base of your spine. This complication is called cauda equina syndrome (CES). Pressure on the nerves in your lower spine can make it hard to control urination or bowel movements.

Weakness and numbness in your legs are other signs of CES. If you have these symptoms, see a neurologist for an exam.

The main symptoms of AS are pain and stiffness in your lower back, buttocks, and hips. Yet it is possible to have more unusual symptoms, including eye pain, a swollen jaw, and appetite loss.

No matter what symptoms you have, see a doctor for treatment. Drugs like NSAIDs and biologics help bring down inflammation and relieve symptoms. Depending on what problems you’re having, you may need to see a specialist for other types of treatment.