Introduction
First described clinically in 1904, ankylosing spondylitis (AS) is an autoimmune disease characterized by chronic inflammation of the spine, sacroiliac (SI) joints, and associated soft-tissue structures. With classically insidious onset, AS has an estimated incidence of 1.5-2 million and is most commonly diagnosed before the age of 40 years. Although the predominant symptoms associated with AS are axial back pain and stiffness, patients may also report peripheral joint stiffness and pain, with characteristic "sausage digits," as well as extraskeletal manifestations in line with the systemic inflammatory response, most commonly inflammatory bowel disease, acute anterior uveitis, and psoriasis. The presence of AS also increases the risk for cardiovascular disease and pulmonary manifestations such as restrictive lung disease, likely secondary to fibrosis from chronic inflammation (Dillon & Hirsch, 2011; Elyan & Khan, 2006; National Institute of Health [NIH], 2022; Rudwaleit & Baeten, 2006; Simone et al., 2018; Wenker & Quint, 2022; Winkler & Miller, 2022; Zhu et al., 2019).
Variable rates of progression, with symptoms that are mild, episodic, and self-managed with stretching and over-the-counter medications, many times make early detection difficult. It is estimated that patients are symptomatic for an average of 10 years prior to confirmed diagnosis. For others, a more concerning clinical picture with rapid progression of symptoms causes functional decline and prompts involved diagnostic workup. As there is no cure for AS, the goals of treatment are to alleviate pain, maintain motion and function, and, with the use of pharmacotherapies, prevent disease progression (Dillon & Hirsch, 2011; Elyan & Khan, 2006; NIH, 2022; Rudwaleit & Baeten, 2006; Simone et al., 2018; Wenker & Quint, 2022; Winkler & Miller, 2022; Zhu et al., 2019).
Case Presentation
A 24-year-old woman presented for the evaluation of chronic, progressive, low back pain and stiffness. She was a cheerleader and tumbler through high school and had always attributed her symptoms to those associated activities. She could not recall a day in the last 10 years that was pain free. After graduating, her activity level significantly decreased, with her tumbling only a couple of days a week for about 90 minutes each session. Despite this change in activity level, her symptoms gradually worsened over the next couple of years. This was described as predominantly low back and buttock pain that occurred in the morning, slowly improving throughout the day but never fully resolving. She reported an inability to get out of bed some days due to significant back pain and stiffness. At one point, she was diagnosed with a urinary tract infection but had no notable improvement of the associated back and buttock pains with antibiotic therapy. She eventually saw a chiropractor and was advised to stop tumbling for a time to see whether symptoms would calm down. Unfortunately, she did not have any kind of notable improvement. She started taking daily ibuprofen and acetaminophen, as well as utilizing various topicals, to manage symptoms. Confounding things, during a particular session of chiropractic care, she noted a "yanking" on her leg that caused sudden onset of right hip pain. She was subsequently diagnosed with hip labral pathology by an outside orthopaedist who took her for arthroscopic repair. She reported that surgeon had explained the other ongoing symptoms were unrelated to the labral pathology and had referred her for further evaluation of potential spinal stenosis.
In further discussing other ongoing symptoms, she noted chronic fatigue without restful sleep as well as night sweats that occurred about once a week. She had never checked her temperature. She also had several food "sensitivities," although not formally diagnosed with any gastrointestinal pathology. Her family history was significant for a father who had multiple spine surgeries by the age of 40 years and a maternal grandmother with rheumatoid arthritis. She was not absolute as to the underlying reason for her father's multiple surgeries but was sure it was not traumatic.
Upon presentation was an alert, oriented, affect-appropriate, overweight female in no apparent distress. She ambulated with a steady gait, without use of an assistive device. She was able to heel-and-toe walk in coordinated fashion but noted lower back and buttock pain with toe walking. Inspection revealed an anterior pelvic tilt with increased lumbar lordosis and a slight forward trunk lean. There was no notable swelling, scars, or discoloration. She displayed a grossly symmetrical lumbar range of motion, with hands easily touching the floor, but with noted pain and "pressure" that extended into her buttocks. Her strength was 5/5 throughout bilateral lower extremities. She was found to be distally neurovascularly intact with symmetric, brisk reflexes. She had reproduced hip pain with FABER and FADIR testing on the right and FADIR only on the left. Both SI thrust and lateral compression were positive. Stinchfield maneuver produced posterior pain bilaterally, whereas bilateral straight leg raise and slump were negative.
The patient had provided outside radiographs of the lumbar spine, pelvis, and sacrum/coccyx to review at time of consultation (see Figure 1). There was no apparent acute osseous abnormality, with the straightening of lumbar lordosis favored to be secondary to supine positioning.
Management
Initial management included a lumbar exercise and stretching program, referral to physical therapy, and a tapering dose of oral prednisone, which was followed by resumption of ibuprofen. She was to avoid repetitive impact activities and keep a log of her symptoms. It was also recommended she contact her primary care provider to check laboratory test results in assessing for other underlying causes of noted fatigue and recurrent night sweats (NIH, 2022; Wenker & Quint, 2022; Winkler & Miller, 2022).
Five weeks later, the patient followed up, reporting continued symptoms. She noted initial improvement with the steroid taper but the effects had worn off, "untouched" by the ibuprofen taken the following 2 weeks. The week prior she had 2 days when she could not tolerate getting out of bed. She again reported night sweats but had not checked her temperature. She reported the laboratory workup performed by primary care was "normal" and likely poor diet and inconsistent sleep habits were the underlying cause of her fatigue.
Her examination was again most remarkable for provoked bilateral SI pain and so was recommended she proceed with magnetic resonance imaging (MRI) of the pelvis (see Figure 2). This MRI revealed symmetric sclerosis, with mild bone marrow edema, of bilateral SI joints. With these findings, the patient was referred to interventional radiology for SI joint steroid injections, counseled on continued use of medications, and encouraged to continue with home stretching and exercise program. She was also referred back to her primary care for additional laboratory workup and was recommended to see a rheumatologist for further evaluation. The full rheumatologic workup, which included elevated inflammatory markers and positive HLA B27, was confirmatory for AS, and the patient was subsequently started on biological therapy by her rheumatologist (Elyan & Khan, 2006; NIH, 2022; Reveille & Weisman, 2013; Wenker & Quint, 2022; Winkler & Miller, 2022).
Discussion
Back pain is a common complaint with numerous potential etiologies. Thorough history should make evident whether the symptoms fit the classic presentation of mechanical back pain, which includes pain that worsens with activities and improves with rest, with or without prior trauma, versus those of inflammatory back pain (IBP), which are typically described as worsening stiffness and aching with rest that improves with exercise and use of anti-inflammatory medications. Suspicions should be raised when a young patient reports chronic symptoms. With the advancement of imaging techniques, notably the sensitivity of MRI in assessing for marginal sclerosis and bone marrow edema, it has become easier to detect and appropriately diagnosis IBP conditions such as AS. It is important to note though that the presence of SI joint changes in isolation is not diagnostic for IBP as they are known to occur during flares of mechanical back pain as well as in asymptomatic patients (Dillon & Hirsch, 2011; Elyan & Khan, 2006; NIH, 2022; Simone et al., 2018; Wenker & Quint, 2022; Winkler & Miller, 2022; Zhu et al., 2019).
Of even greater consequence to future potential treatments are the advancements in laboratory analysis in reliably assessing for and isolating specific inflammatory and immune markers that play key roles in the ongoing inflammatory process. Biological therapy is currently the mainstay of medical treatment, with the primary goal of preventing the progression of AS. The discovery of numerous genetic markers, including HLA B27 and ERAP1, shows promise in aiding in earlier detection and ability to start treatment. As with imaging findings, the presence of these markers alone is not sufficient for diagnosis and must be used in combination with the patient's history, clinical presentation, as well as other laboratory and diagnostic imaging findings to confirm the appropriate diagnosis (Elyan & Khan, 2006; NIH, 2022; Reveille & Weisman, 2013; Simone et al., 2018; Wenker & Quint, 2022; Winkler & Miller, 2022; Zhu et al., 2019).
References