Musculoskeletal masqueraders

Initial presentation

• Generalised muscle or joint pain
• Debilitating fatigue
• Reduced cognition / concentration / "brain fog"

Axial Spondyloarthropathy (AxSpA) — screening criteria

Low back pain that started before age 45 and lasting over 3 months, with any of:

• Morning stiffness >1 hour
• Pain waking patient in the second half of the night
• Alternating or persistent buttock pain
• Improves with movement, worsens with rest
• Improves within 48 hours of NSAIDs
• First-degree relative with spondyloarthritis
• Current or past arthritis
• Current or past enthesitis
• Current or past psoriasis

Useful tools:

• Symptom checker: actonaxialspa.com/symptoms-checker
• SPADE Tool: spadetool.co.uk

Spondyloarthropathy (SpA) — key clinical features

Inflammatory pain (worse in the morning lasting over 30 min, better on movement, worse with rest) with:

• Asymmetrical joint involvement
• Dactylitis — swelling of an entire finger or toe (sausage digit)
• Enthesitis — most commonly Achilles tendonitis or plantar fasciitis
• Recurrent or persistent peripheral arthritis

Extra-articular features:

• Psoriasis
• Inflammatory bowel disease
• Uveitis
• Family history of SpA

Connective Tissue Disease (CTD) — screening features

• Malar / butterfly rash
• Photosensitivity
• Recurrent mouth ulcers
• Diffuse alopecia
• Raynaud's disease
• Sicca symptoms (dry eyes, dry mouth)
• Lymphadenopathy
• No diurnal pattern to symptoms

Lyme disease — screening features

• Flu-like illness prior to symptom onset
• Tick exposure or risk of tick exposure (see below)
• Rash prior to symptom onset — note that not all Lyme rashes have the bullseye appearance and not everyone develops a rash (CDC rash poster)
• Widespread ache/pain without inflammatory signs
• Non-dermatomal numbness or paraesthesia

AxSpA

• 4 or more screening criteria → refer to Rheumatology
• 3 criteria → request HLA-B27 and other bloods as appropriate; refer to Rheumatology if positive

SpA

• Assess for inflammatory features and extra-articular signs as above
• Bloods as appropriate (FBC, ESR, CRP, U&E)
• Note that normal bloods do not exclude SpA

Connective Tissue Disease

• Request bloods including ANA, FBC, ESR, CRP, U&E and urine dip; add other bloods as clinically indicated

Lyme disease

• Request Lyme serology (NHS-accredited lab) and other bloods as appropriate; consider BBV testing
• Sensitivity can be limited, especially in the immunocompromised
• Antibiotics may be started before serology results if clinical suspicion is strong (results can take several weeks) — see NICE CKS Lyme disease
• Signpost to Lyme Resource Centre

Rheumatology — AxSpA

• 4 or more screening criteria, or
• 3 criteria with positive HLA-B27

Rheumatology — SpA

• Dactylitis, persistent joint pain and swelling, or enthesitis with a history of psoriasis, inflammatory bowel disease or uveitis
• HLA-B27 positive with symptoms
• Clinical suspicion remains high despite normal blood tests

Rheumatology — CTD

• Raised ANA / inflammatory markers, or
• Clinical suspicion remains high despite normal blood tests

Lyme disease — onward referral

• Ongoing symptoms despite 2 courses of antibiotics with positive serology → refer to Dr Sharon Irvine OPAT (outpatient antibiotic) service as per NICE guidance
• Strong clinical suspicion but negative serology → discuss with Infectious Diseases / Microbiology regarding further testing
• Ongoing symptoms with negative bloods and no strong clinical suspicion of Lyme → refer to the appropriate specialty for the dominant symptom (e.g. joint pains → Rheumatology; neuropathy → Neurology)