Spondyloarthropathies — Written Clinical Reasoning

SAQ 1 — Integrated Management of Newly Diagnosed Ankylosing Spondylitis (20 marks, 30 minutes)

Prompt: Outline your integrated management plan for this patient with newly diagnosed, active ankylosing spondylitis, including: (a) the classification criteria confirming the diagnosis; (b) the treatment ladder and first-line pharmacological therapy with exact drug, dose, route, frequency and rationale; (c) the role of physiotherapy and exercise; (d) the indications for biologic therapy and the drug classes available, with the landmark trial evidence; (e) pre-biologic screening; and (f) the management of his uveitis risk and the fracture safety counselling. [1]

Model Answer

(a) Diagnosis confirmation — modified New York and ASAS criteria (3 marks): [1]

This patient meets both the modified New York criteria for ankylosing spondylitis and the ASAS classification criteria for axial spondyloarthritis [1][2]. The modified New York criteria require radiographic sacroiliitis (grade 2 bilateral or grade 3 to 4 unilateral) plus at least one clinical criterion. He has bilateral grade 2 sacroiliitis on pelvic radiograph plus inflammatory back pain (the first clinical criterion) and a family history of SpA in a first-degree relative (supporting). The ASAS imaging arm is satisfied: sacroiliitis on imaging plus at least one SpA feature — he has several (inflammatory back pain, enthesitis/heel pain, uveitis, family history, elevated CRP, HLA-B27 positivity).

The clinical features of inflammatory back pain are classical: insidious onset, age under 45, improvement with exercise, no improvement with rest, night pain, alternating buttock pain, morning stiffness over 30 minutes. His objective measures confirm active, significant disease: BASDAI 6.2 (threshold 4 for active disease), ASDAS-CRP 3.4 (high disease activity), elevated CRP, reduced modified Schober (3 cm, abnormal — normally above 5 cm), and occiput-to-wall distance 4 cm (abnormal — normally 0 cm). [1]

(b) Treatment ladder and first-line pharmacological therapy (4 marks): [1]

NSAIDs are the first-line pharmacological treatment per the ASAS-EULAR 2022 recommendations [4]. This patient has failed adequate trials of two NSAIDs (ibuprofen at a sub-therapeutic dose of 1.2 g/day and naproxen at a full dose of 1 g/day for 4 weeks each), which is the standard threshold for biologic escalation.

Before escalating, I would ensure he has had an adequate trial of at least one NSAID at full anti-inflammatory dose — ibuprofen at 400 to 800 mg three times daily (2.4 g/day), or diclofenac 75 mg twice daily, or celecoxib 200 mg twice daily. His ibuprofen trial was sub-therapeutic (only 1.2 g/day). I would trial diclofenac 75 mg twice daily or celecoxib 200 mg twice daily for 4 weeks before concluding NSAID failure. [1]

However, given his high disease activity (ASDAS 3.4), objective inflammation (elevated CRP, sacroiliitis), and significant functional limitation (reduced spinal mobility, carpenter unable to work effectively), he is a clear candidate for biologic therapy. The Poddubnyy cohort data support continuous high-dose NSAID use to retard radiographic progression [6], but he has not responded adequately.

(c) Role of physiotherapy and exercise (3 marks): [1]

Physiotherapy and exercise are as essential as pharmacological therapy in AS management and are mandated by the ASAS-EULAR recommendations [4]. I would refer him to a physiotherapist experienced in SpA for:

• Supervised group exercise — evidence shows this is superior to home exercise for maintaining spinal mobility and function
• Daily postural exercises — to prevent the progressive flexion deformity characteristic of advanced AS (his occiput-to-wall distance of 4 cm indicates early thoracic kyphosis)
• Spinal mobility exercises — modified Schober exercises, rotation, extension to maintain movement
• Strengthening exercises — core and paraspinal strengthening to support posture
• Swimming — ideal exercise: low-impact, promotes extension, rotation and chest expansion
• Deep breathing exercises — to maintain chest expansion

I would explain that exercise is treatment, not optional — the single most important self-management strategy. The message is: NSAIDs and biologics control the inflammation; physiotherapy and exercise maintain the mobility. [1]

(d) Biologic therapy — indications, classes and evidence (4 marks): [1]

This patient meets the criteria for biologic therapy: active disease (ASDAS at least 2.1, BASDAI at least 4) despite an adequate trial of at least two NSAIDs [4]. Two biologic classes are available as first-line:

TNF inhibitors — adalimumab 40 mg subcutaneously every 2 weeks, etanercept 50 mg subcutaneously weekly, infliximab 5 mg/kg IV, certolizumab pegol, or golimumab 50 mg monthly. The landmark evidence: Braun et al. (2002) showed infliximab dramatically improved disease activity in AS (53 per cent of infliximab-treated patients achieved at least 50 per cent regression of disease activity at week 12 versus 9 per cent of placebo) [5].

IL-17 inhibitors — secukinumab 150 mg subcutaneously weekly for 4 weeks then monthly, or ixekizumab. The MEASURE 1 trial (Baeten et al., 2015) showed secukinumab achieved ASAS20 response in 60 per cent at week 16 versus 29 per cent of placebo [3].

Drug choice for this patient: Given his history of uveitis, I would prefer a monoclonal antibody TNF inhibitor (adalimumab 40 mg subcutaneously every 2 weeks) over etanercept (which is ineffective for uveitis and may worsen it) or an IL-17i (which has a more modest uveitis-reducing effect). Adalimumab is effective for axial symptoms, peripheral arthritis, uveitis prevention, and is relatively safe. His HLA-B27 positivity and history of uveitis are strong indications for adalimumab. [1]

(e) Pre-biologic screening (3 marks): [1]

Before starting adalimumab, the full pre-biologic screen:

1. IGRA (QuantiFERON-TB Gold) and chest X-ray — latent TB reactivation is the most feared complication of monoclonal TNFi. If IGRA is positive, treat with rifampicin 600 mg daily for 4 months or isoniazid 300 mg daily for 9 months for at least 1 month before starting adalimumab.
2. Hepatitis B serology (HBsAg, anti-HBs, anti-HBc) — prophylactic antivirals if HBsAg positive.
3. Hepatitis C and HIV serology.
4. FBC, U&E, LFTs — baseline.
5. Vaccinations — ensure up to date before starting: influenza, pneumococcal (23-valent polysaccharide and 13-valent conjugate), hepatitis B, recombinant zoster (Shingrix), COVID-19. Avoid live vaccines once on biologics.
6. Cardiac assessment — TNFi caution in NYHA III/IV heart failure; check for symptoms.
7. Lipids and HbA1c — baseline. [1]

(f) Uveitis risk and fracture safety counselling (3 marks): [1]

Uveitis: He has already had one episode. I would counsel him to recognise the symptoms (unilateral painful red eye, photophobia, blurred vision) and to seek same-day ophthalmology review if they recur — delayed treatment risks permanent synechiae and visual loss. The adalimumab he is starting will reduce uveitis recurrence. I would provide a letter for him to show any emergency department or optometrist, stating his diagnosis and the urgency of slit-lamp examination. [1]

Spinal fracture: I would counsel him that the inflammatory process in AS can cause the spine to become stiff and, over time, more brittle. He should understand that even a minor fall — from a height, a bicycle, or at work — could cause a serious spinal fracture, and that he must present to the emergency department for full spine imaging (CT and potentially MRI) after any significant trauma, even if he feels well. This is a safety-critical message, particularly important for a carpenter who works at heights. I would document this counselling in his medical record. [1]

SAQ 2 — Psoriatic Arthritis with Polyarticular Disease (10 marks)

Prompt: A 42-year-old woman presents with a 6-month history of asymmetrical pain and swelling in her right second DIP, left third PIP, both wrists and right knee, with two sausage digits on her right hand. She has pitting and onycholysis of multiple fingernails. She has scalp psoriasis. RF is negative. CRP is 28 mg/L. Hand X-rays show pencil-in-cup deformity at the right second DIP and juxta-articular new bone formation. She scores 5 on the CASPAR criteria. Discuss your approach, including diagnosis confirmation, disease activity assessment (DAPSA), the treatment ladder, and the specific role of IL-23 inhibitors versus IL-17 inhibitors and TNF inhibitors. [1]

Model Answer

(a) Diagnosis — CASPAR criteria (2 marks): [1]

This patient meets the CASPAR criteria for psoriatic arthritis [1] />. The prerequisite (established inflammatory articular disease) is met. Her score: current psoriasis (scalp) = 2 points; psoriatic nail dystrophy (pitting, onycholysis) = 1 point; negative RF = 1 point; current dactylitis (sausage digits) = 1 point; radiographic juxta-articular new bone formation = 1 point. Total: 6 points (threshold is 3 or more). The CASPAR criteria have a sensitivity of 91 per cent and specificity of 99 per cent for PsA.

The pencil-in-cup deformity at the DIP is pathognomonic for psoriatic arthritis and distinguishes it from the DIP osteoarthritis (Heberden nodes) that lacks the erosive, pencil-in-cup morphology. [1]

(b) Disease activity assessment — DAPSA (2 marks): [1]

I would calculate the DAPSA (Disease Activity index for Psoriatic Arthritis), which sums: tender joint count (68), swollen joint count (66), patient pain VAS (0 to 10), patient global activity VAS (0 to 10), and CRP (mg/dL). Given her multiple tender and swollen joints, elevated CRP and likely high pain and global VAS, her DAPSA would be in the moderate-to-high disease activity range (above 14). The treatment target is a DAPSA of 4 or below (remission or low disease activity). I would also assess skin disease with the PASI (Psoriasis Area and Severity Index) and body surface area involvement. [1]

(c) Treatment ladder (3 marks): [1]

For this patient with moderate-to-severe polyarticular PsA:

1. NSAIDs — naproxen 500 mg twice daily for symptomatic control.
2. csDMARD — methotrexate 15 mg orally once weekly (with folic acid 5 mg weekly), titrating to 20 to 25 mg weekly, is first-line for polyarticular PsA. It treats both the joints and, partially, the skin. Monitor FBC, LFTs, creatinine.
3. If target not met in 3 to 6 months — escalate to a biologic. Given her significant skin disease (scalp psoriasis with nail involvement), an anti-IL-17 (secukinumab or ixekizumab) or anti-IL-23 (ustekinumab or guselkumab) would be preferred over a TNFi because they are more effective for skin clearance. Alternatively, a TNFi (adalimumab) is effective for both joints and skin and is also appropriate. [1]

(d) IL-23 vs IL-17 vs TNF inhibitors — the key distinction (3 marks): [1]

This is a critical exam point for PsA:

• IL-23 inhibitors (ustekinumab — anti-IL-12/23 p40; guselkumab — anti-IL-23 p19) are effective for the skin and peripheral joints of PsA but NOT approved for axial SpA. If this patient has axial involvement (sacroiliitis), an IL-23i alone would be inadequate.
• IL-17 inhibitors (secukinumab, ixekizumab) are effective for both skin and axial/peripheral joints — the best single agent for PsA with prominent skin disease and any axial component. Caution: they may exacerbate IBD.
• TNF inhibitors (adalimumab, etanercept) are effective for joints, skin, uveitis, and IBD (except etanercept for IBD). Adalimumab is a good all-round choice. [1]

For this patient, without axial involvement documented, any of the three classes is appropriate. If she has prominent skin disease (PASI above 10), an IL-17i (secukinumab) or IL-23i (guselkumab) would be preferred for superior skin clearance. If she has recurrent uveitis or co-existing IBD, a monoclonal TNFi (adalimumab) would be preferred, with IL-17i avoided in IBD. [1]