Polyarthitis

Diagnosing Polyarthritis

This past week we discussed the approach to polyarthritis. Here are the key points to keep in mind:

Key Lessons:

1. History of the Arthritis

The pattern, timing, and location of the joints affected are key to determining a diagnosis. Establish whether the complaint is articular (pain in all directions of movement, pain on passive movement) or peri-articular (pain in some ranges of motion, no pain on passive movement). Establish whether the arthritis is inflammatory (morning stiffness, systemic symptoms, joint swelling, limited range of motion) or non-inflammatory. Document the affected areas carefully on a diagram, for example:

1. Symmetric large joint: Seronegative arthropathy, rheumatoid arthritis

2. Asymmetric oligoarthritis: Seronegative arthropathy, infectious, or crystal induced

3. Symmetric small and large joints (non-inflammatory): Osteoarthritis

4. Symmetric small and large joints (inflammatory): Seropositive arthropathy, psoriatic arthritis

2. Establish a Differential Diagnosis:

Inflammatory conditions:

Seropositive conditions: Rheumatoid Arthritis, MCTD, Systemic Lupus Erythematosus, DM/PM

Seronegative condtions (Spondyloarthritidies): Anklyosing Spondylitis, Reactive Arthritis, Psoriatic arthritis, and IBD associated.

Systemic vasculitis

Crystal disease

Non-Inflammatory:

Osteoarthritis

Hemochromatosis

Acromegaly

Infectious:

Bacterial: S. aureus, Group G strep, Neisserial infections

Viral: Rubella, Parvovirus, HIV, Hepatitis B/C

Tick borne disease: Lyme disease (Borrelia burgdorferi)

Rheumatic Fever

Endocarditis 

Other Rarer Inflammatory Causes

Sarcoidosis

Palindromic rheumatism

Serum sickness

3. Associated symptoms

In order to narrow down your differential diagnosis, inquire about associated (extra-articular) symptoms:

Seropositive Disease: Malar rash, photosensitive rash, oral ulcers, sicca symptoms, nodules, Raynaud's phenomenon

Seronegative Disease (Spondylarthritis): low back pain, uveitis, diarrhea, enthesitis, psoriatic plaques, dactylitis.

Infectious: diarrhea illness, recent STI, recurrent fevers, cellulitic rash.

Osteoarthritis: No associated or systemic symptoms.

4. Investigations

- Bloodwork: CBC (screen of inflammatory or systemic disorder), serum urate (if gout is suspected), creatinine and urea (can help establish systemic involvement of a disorder), rheumatologic tests such as complement/ANA/ANCA/ESR (should only be ordered if a rheumatologic condition are highly suspected).

- Arthrocentesis: Can very be very helpful in establishing a diagnosis if fluid is present in one of the affected joints. Would likely be helpful in an acute on chronic process

- Imaging: Plain films are helpful if process is longstanding and underlying changes have developed.

Resources;

Click here for a review article on polyarthritis from CMAJ in 2000.

Click here for a review article on polyarthritis and fever from the NEJM from 1994.