Abstract
Introduction
Ankylosing spondylitis (AS) is the most common form of axial spondyloarthritis, diagnosed by radiographic sacroiliitis under the modified New York criteria. Although classic AS typically begins in early adulthood, late-onset AS (LoAS) defined as symptom onset after age 45, accounts for approximately 3.5–13.8% of cases. LoAS often presents with higher disease activity and greater peripheral involvement, yet little is known about its MRI characteristics and management. We report a 73-year-old male with HLA-B27 positive AS, symptomatic back pain, MRI-confirmed sacroiliitis, peripheral entheseal disease, and multiple comorbidities, illustrating diagnostic and treatment challenges in this rare age group.
Case description
A 73-year-old man presented to the rheumatology clinic with inflammatory back and neck pain, scoring 5/10 on the spinal visual analogue scale(VAS). He also reported bilateral Achilles and right elbow pain.
His medical history included recurrent uveitis, hypothyroidism, prior inguinal hernia repair, resolved dermal sarcoma, anaemia of chronic disease, and asymptomatic urinary tract colonisation due to a urethral stent post-urethrotomy with ongoing self-dilatation. He experienced six uveitis episodes every two years over 10–15 years, leading to a positive HLA-B27 result five years ago. Notably, his son was diagnosed with AS in his late 20s. He denied psoriasis or inflammatory bowel disease. He was a non-smoker and consumed minimal alcohol (2-4 units/week).
On examination, he had reduced lumbar flexion and tenderness in the medial aspect of the right elbow. He also had tenderness in the Achilles tendon. Investigations raised CRP of 13 mg/L. with baseline normal renal, liver function and full blood count. MRI of the spine and sacroiliac joints showed chronic sacroiliitis with extensive erosions and sclerosis, along with inflammatory changes at the costovertebral and costotransverse junctions correlating with his thoracic pain. Ultrasound of the left ankle revealed insertional Achilles tendinopathy, retrocalcaneal bursitis, and mild distal peroneal tenosynovitis leading to the diagnosis of AS.
His disease activity was high with BASFI (Bath Ankylosing Spondylitis Functional Index) was 7.8 and BASDAI (Bath Ankylosing Spondylitis Disease Activity Index) was 7.6.
Initial management included 120 mg intramuscular methylprednisolone, followed by a tapering prednisolone course (from 20 mg daily). Tramadol was prescribed for nocturnal pain. NSAIDs were avoided due to cardiovascular and renal risks. At follow-up, spinal VAS improved to 3–4 and labs remained stable. The patient consented to starting adalimumab, pending ongoing infection monitoring. His axial and peripheral symptoms are eased and he is currently in remission.
Discussion
This case highlights the diagnostic challenges of late-onset ankylosing spondylitis (LoAS). The patient reported pain radiating from the skull to the shoulders, accompanied by morning stiffness for several years, unrelieved by ibuprofen or physiotherapy. LoAS presents unique diagnostic and therapeutic dilemmas. While most AS cases begin before age 30, about 15% manifest after 45. LoAS is often associated with higher disease activity, more peripheral involvement, and diagnostic delay. LoAS is associated with higher disease activity, more peripheral arthropathy, and diagnostic delay. Radiographic sacroiliitis remains crucial for diagnosis, but age-related degenerative and osteoarthritic changes can obscure imaging findings. MRI is important in differentiating inflammatory sacroiliitis from degenerative alterations, as demonstrated here with classic axial and entheseal inflammation.
Management in this population requires careful consideration of age-related comorbidities. Although NSAIDs are first-line therapy for AS, their gastrointestinal, renal, and cardiovascular risks often limit their use in elderly patients. Biologics, particularly TNF inhibitors, offer effective disease control, but data on their safety and efficacy in LoAS are limited. Studies suggest reduced treatment response and drug retention in older adults, likely due to immunosenescence, coexisting conditions, and increased infection risk.
In this case, short-term corticosteroids and tramadol were initiated while NSAIDs were avoided. Given chronic urinary tract colonisation and planned immunosuppression, input from urology allowed pre-emptive infection planning. A shared decision was made to initiate adalimumab, with infection monitoring in place.
This case illustrates the need for a tailored, multidisciplinary approach in LoAS. MRI plays a pivotal role in diagnosis when radiographic changes are inconclusive. While biologics can be highly effective, their use in older patients must balance therapeutic benefit against potential harm. There remains a critical need for more evidence to guide bDMARD use specifically in the elderly with AS, as current treatment strategies are largely based on data from younger populations.
Key learning points
1. Late-onset AS is uncommon but should be considered in elderly patients presenting with chronic back pain. Although AS classically begins in early adulthood, up to 13.8% of cases may present after age 45. Our patient presented with peripheral and axial involvement of AS.
2. MRI is invaluable for distinguishing inflammatory versus degenerative changes in elderly spines. Radiographic sacroiliitis and axial features may be obscured by age-related changes. MRI enabled diagnosis in our patient by demonstrating active sacroiliitis and costovertebral inflammation.
3. LoAS typically demonstrates higher disease activity and more peripheral entheseal involvement. Our case combined axial inflammation, costovertebral involvement, and peripheral tendon pathology, aligning with literature that patients >45 years often exhibit a broader SpA phenotype which responded well to the steroids and biologics treatment.
4. Pharmacotherapy must account for age-related comorbidities and polypharmacy. NSAIDs, although first-line in younger cohorts, bear unacceptable side effects in the elderly. Biologics are effective but may have attenuated response and tolerability in older patients due to comorbidities and immunosenescence.
5. A short course of corticosteroids can serve as a practical interim measure for symptom control. In this case, methylprednisolone followed by a structured prednisolone taper effectively managed inflammation and pain while minimising long-term risks, particularly in the context of renal and gastrointestinal vulnerabilities.
6. Further research is needed in LoAS. MRI phenotypes, optimal management strategies, and outcomes in LoAS remain under-studied. Such cases help expand awareness and guide future evidence.