576 - Dissecting the Outpatient Clinical Zebra: A Case of Late-Onset Ankylosing Spondylitis

Friday, February 23, 2024

5:00 PM – 6:30 PM EDT

Presenting Author(s)

DC

Dorothy Anne G. Cabantan, BS

Medical Student
Michigan State University College of Osteopathic Medicine
Ann Arbor, Michigan, United States

Co-Author(s)

UA

Usman Ashraf, MD

Attending Physician
Associates in Physical Medicine and Rehabilitation, PC | Trinity Health-Ann Arbor
Ypsilanti, Michigan, United States

Case Diagnosis: Late-Onset Ankylosing Spondylitis

Case Description: The patient was a 46-year-old male who presented to an outpatient PM&R clinic for progressively worsening, “jolt-like” low back pain radiating to his abdomen, with decreased cervical, lumbar, and bilateral lower extremity mobility. He was otherwise healthy with previously negative imaging, except for two decades of low blood pressure and chronic back pain following a remote injury. Due to excruciating pain for two weeks, he presented to the emergency department where images were negative except for incidental ankylosis of the bilateral sacroiliac joints with squaring of the vertebral bodies, and early bridging of the syndesmophyte formation. To further investigate, PM&R obtained dedicated spine x-rays revealing ankylosing spondylitis, with positive HLA-B27, elevated ESR, and CRP, thus confirming the diagnosis. PM&R promptly started the patient on TNF inhibitor therapy with a referral to Rheumatology, and rehabilitative measures focused on PT, OT, and a home exercise regimen.

Discussions: Ankylosing Spondylitis (AS) is commonly identified prior to age 30 with only < 5% of patients diagnosed after age 45. Common manifestations include decreased spinal mobility and peripheral arthritis, though co-morbidities may include autonomic dysfunction, inflammatory bowel disease, uveitis, and psoriasis. Its broad symptomatology, disease duration, and the genetic variability across patient populations can make prompt identification and diagnosis difficult. For instance, HLA-B27 is correlated with AS, however genetic variability exists across ethnic groups and thus can be negative. Additionally, elevated CRP and ESR, and x-rays demonstrating a “bamboo spine” and bilateral sacroiliitis are pathognomonic. Further research is imperative for early disease detection to optimize treatment outcomes and slow deterioration with rehabilitative efforts.

Conclusions: This case emphasizes the importance of prompt diagnosis and treatment of ankylosing spondylitis, and while patients do not necessarily fit the standard clinical picture, benefit from screening to kickstart rehabilitation and improve functional outcomes.