AS in Women: Why the Diagnosis Is Often Delayed or Mistaken for Fibromyalgia

Ankylosing Spondylitis in Women: Why the Diagnosis Is Often Delayed or Mistaken for Fibromyalgia

Ankylosing Spondylitis (AS) is a chronic inflammatory form of arthritis that primarily affects the spine and sacroiliac joints. For many years, it was considered a condition that mostly affected men. We now know that this view was incomplete—and for many women, it has led to delayed, missed, or incorrect diagnoses.

One of the most common misdiagnoses in women is fibromyalgia. While both conditions can cause widespread pain and fatigue, they are not the same illness, and confusing one for the other can delay appropriate treatment. Understanding why this happens is an important step toward better care and better outcomes.

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Why Ankylosing Spondylitis Is Harder to Recognize in Women

1. Symptoms Often Look Different Than “Classic” AS

Traditional medical teaching described Ankylosing Spondylitis as:

• Young men
• Severe lower back pain
• Visible spinal damage on X-rays
• Progressive spinal fusion

Many women do not fit this pattern.

In women, AS is more likely to cause:

• Neck, shoulder, and upper back pain
• Pain that moves from one area to another
• Less obvious spinal stiffness
• More fatigue than back pain
• Pain in hips, knees, ankles, or feet

Because these symptoms are less “textbook,” they may not immediately raise suspicion for Ankylosing Spondylitis.

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2. Inflammation Is Often Less Visible on Imaging

Standard X-rays may appear normal for many years, especially in women.

• Women with AS are more likely to have non-radiographic axial spondyloarthritis, meaning inflammation exists but does not yet show on X-ray.
• MRI scans can detect early inflammation, but they are not always ordered early in the diagnostic process.

When imaging does not show obvious damage, symptoms may be dismissed or attributed to other causes.

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3. Pain Is More Likely to Be Labeled as Fibromyalgia

Fibromyalgia is a real and serious condition, but it is not inflammatory. It is characterized by:

• Widespread muscle pain
• Tender points
• Fatigue
• Poor sleep
• Brain fog

Women with Ankylosing Spondylitis may experience all of these symptoms, especially early in the disease.

Key differences that are often missed:

• AS pain typically improves with movement, not rest
• Morning stiffness lasts longer than 30–60 minutes
• Pain may wake someone in the second half of the night
• Blood tests may show inflammation (though not always)

When inflammation is subtle or overlooked, fibromyalgia may be diagnosed instead.

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The Role of Gender Bias in Diagnosis

Research shows that women’s pain is more likely to be under-recognized or minimized. Symptoms may be described as:

• Stress-related
• Emotional
• Hormonal
• “Just chronic pain”

This does not mean doctors intend harm, but long-standing biases can affect diagnostic thinking. Ankylosing Spondylitis may simply not be considered early enough in women.

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Why Delayed Diagnosis Matters

Delayed diagnosis of Ankylosing Spondylitis can lead to:

• Ongoing inflammation that damages joints over time
• Reduced mobility and flexibility
• Increased fatigue and reduced quality of life
• Emotional distress from not being believed or understood

Early diagnosis allows for treatment that can reduce inflammation, relieve pain, and slow disease progression.

This is not about creating fear—but about recognizing that earlier care usually leads to better outcomes.

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Signs That Ankylosing Spondylitis May Be Missed

Women who are eventually diagnosed with AS often report years of symptoms before receiving answers. Common clues include:

• Chronic back or pelvic pain starting before age 45
• Pain that improves with activity but worsens with rest
• Long-lasting morning stiffness
• Pain that wakes you at night
• Alternating buttock pain
• Family history of inflammatory arthritis
• Poor response to standard pain medications

Having some of these signs does not mean you have Ankylosing Spondylitis—but they are worth discussing with a healthcare professional.

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Fibromyalgia vs. Ankylosing Spondylitis: Key Differences

While overlap exists, there are important distinctions:

Fibromyalgia

• Not caused by inflammation
• Pain is widespread and constant
• Imaging and blood tests are usually normal
• Exercise may worsen pain initially

Ankylosing Spondylitis

• Caused by immune-driven inflammation
• Pain often centers around the spine and joints
• May show inflammation on MRI or blood tests
• Movement usually helps reduce stiffness

Some people can have both conditions, which makes diagnosis even more complex.

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Why Self-Advocacy Is Important

Many women with Ankylosing Spondylitis report that diagnosis only happened after:

• Seeking a second or third opinion
• Asking directly about inflammatory arthritis
• Seeing a rheumatologist
• Tracking symptoms over time

Keeping a simple symptom log—pain location, stiffness duration, sleep impact, and response to movement—can be helpful during medical visits.

You may also consider doing a free, online symptom check for Medically approved LLM Symptom Checker Chat Bot as a starting point to organize your symptoms before speaking with a clinician.

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Getting the Right Medical Evaluation

If Ankylosing Spondylitis is suspected, a doctor may consider:

• Detailed symptom history
• Physical exam focusing on spinal mobility
• Blood tests for inflammation markers
• Genetic testing (such as HLA-B27, though not required)
• MRI imaging of the sacroiliac joints

Not all tests are positive in all people. Diagnosis is based on the whole clinical picture, not a single result.

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Living Well While Seeking Answers

Waiting for a diagnosis can be frustrating. While you are seeking clarity:

• Gentle, regular movement is often beneficial
• Prioritize sleep and pacing daily activities
• Manage stress in realistic ways
• Seek support from people who listen and believe you

These steps do not replace medical treatment—but they can support overall well-being.

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A Final, Important Note

Persistent pain, stiffness, or fatigue is not something you have to ignore or “push through.” If symptoms interfere with daily life, work, sleep, or mobility, it is important to speak to a doctor, especially about anything that could be serious or life-threatening.

If you ever experience sudden weakness, loss of bowel or bladder control, chest pain, severe eye pain or vision changes, or symptoms that rapidly worsen, seek urgent medical care.

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The Bottom Line

Ankylosing Spondylitis in women is often misunderstood, underdiagnosed, or mistaken for fibromyalgia due to differences in symptom patterns, imaging findings, and long-standing assumptions about who gets the disease. Awareness—by both patients and healthcare providers—is improving, but delays still happen.

You deserve to be heard, taken seriously, and properly evaluated. Asking informed questions, tracking symptoms, and partnering with a healthcare professional can make a meaningful difference in getting the right diagnosis and care.