Ankylosing Spondylitis

Which of the following radiological findings is pathognomonic for advanced ankylosing spondylitis?

A 28-year-old male from Delhi presents with a 3-year history of progressive lower back pain and morning stiffness lasting 2 hours. He reports pain radiating to the buttocks bilaterally and difficulty with spinal flexion. On examination, Schober's test shows 3 cm movement (normal >5 cm). He denies any history of inflammatory bowel disease, uveitis, or psoriasis. Laboratory investigations reveal HLA-B27 positivity, ESR 42 mm/hr, and CRP 8.5 mg/L. Lumbar spine X-ray shows bilateral sacroiliitis with early syndesmophyte formation. What is the most likely diagnosis?

A 35-year-old male with a 6-year history of ankylosing spondylitis presents with acute-onset left eye pain, photophobia, and blurred vision. On slit-lamp examination, there is ciliary injection, aqueous flare, and posterior synechiae. His current AS is well-controlled on NSAIDs and sulfasalazine. Fundoscopy is otherwise normal. What is the most likely ocular complication and the recommended immediate management?

Which HLA allele is most strongly associated with ankylosing spondylitis?