Can Ankylosing Spondylitis Onset Occur After Age 50? - Internal Medicine

Is it possible for ankylosing spondylitis to develop at the age of 50?

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I am a 51-year-old female who has been experiencing significant tightness and stiffness in my hip joint for at least three years.
I initially thought it was due to natural aging, prolonged sitting at work, or improper exercise posture (I have been practicing yoga and aerobic exercise regularly for over 10 years).
In the mornings, it takes me up to 10 minutes or longer to feel some relief.
I often massage and stretch, but the effects are limited.
Two years ago, I had an X-ray of my hip joint in the orthopedics department, which showed no abnormalities.
The year before last, I underwent a health check due to recurrent dry eyes, colds, and diarrhea, which revealed a white blood cell count below the standard.
Last year, I experienced inflammation, redness, swelling, and pain in the distal interphalangeal joints of both hands, leading me to be referred to a rheumatologist for follow-up.
It was unexpectedly discovered that I am HLA-B27 positive.
Over the past two years, I have had blood tests twice; my white blood cell count has increased but remains below the standard.
However, both times, my CRP and ESR levels were normal.
The doctor believes that ankylosing spondylitis would not manifest at my age, and I have not sought further medical attention.
I do not have a clear family history; my father experienced frequent knee and ankle joint inflammation during his military service, which allowed him to avoid marching.
Before he turned 60, he often had red eyes and knee pain but was reluctant to seek medical care, opting for heat therapy or topical ointments instead.
In recent years, these issues seem to have subsided.

In the past six months, the stiffness in my hip area has worsened significantly.
After sitting for 10 minutes, I have to be careful when moving to stand up.
The tightness extends to my buttocks, the back of my thighs, and behind my knees, causing a strong pulling sensation even when walking.
However, after warming up, I can run and stretch freely, but if I remain still for a while and then change positions, the stiffness returns.
Last week, I had an X-ray in orthopedics, which showed no issues with lumbar spine narrowing or slippage.
I later noticed that the painful and stiff area is in the posterior hip joint region, where I can feel two hard spots.
Sometimes the left side hurts more, and after massaging the left side, it feels better, but soon after, the right side experiences increased pain and stiffness.
Yesterday, I bought Celebrex at the pharmacy and took it for the first time.
To my surprise, when I woke up the next morning, the hip joint stiffness and tightness that had troubled me for years had disappeared.
Reflecting on the past, I have had intermittent knee discomfort for the past 10 years, with normal X-rays, so perhaps the source of the problem lies in the hip joint area.

I would like to ask: (1) Is it possible for ankylosing spondylitis to manifest at the age of 50? (2) If CRP and ESR levels are normal, does that mean it is unrelated to ankylosing spondylitis? (3) If I want to clarify what the issue is, which specialty should I consult? The orthopedist found no problems on the X-ray, making it seem like I am faking my illness, and the physical therapy with electrical stimulation and heat has not been effective.
I am willing to pay out of pocket for tests; how should I communicate with the doctor about what tests to request? Thank you!

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Sunny, 50~59 year old female. Ask Date: 2024/05/05