Joint pain in Psoriasis

This case deals with the problem in determining whether joint pain in a subject with Psoriasis is Psoriatic Arthritis or is due to incidental wear and tear or Osteoarthritis

The patient history

The patient was a 56 year old female.

She had a history of nail, scalp and buttock cleft region psoriasis.

She had a two year history of intermittent pains in her neck and her knees.

She reported intermittent pains in multiple other joints.

Sometimes the pain was constant and lasted for a few days.

Sometimes it disturbed her sleep.

Sometimes it was associated with early morning joint stiffness for up to 1 hour.

Anti-inflammatory tablets did not improve things to a significant degree.

There was no reported joint swelling.

The Patient Examination

The patient had scalp psoriasis.

She was obese.

She had some tenderness over the neck.

She had evidence of wear and tear over both knees with joint grinding due to loss of cartilage or what is termed "crepitation".

There was no joint swelling of free fluid evident.

She was also tender over a muscle attachment or muscle enthesis at the brim of the pelvic bones.

Results of Tests

The patients blood tests for Rheumatoid Arthritis and lupus were negative.

Here neck x-ray showed changes of Osteoarthritis.

Her C-reactive protein was elevated at 12mg/L (Normal less than 10mg/L).

The Diagnostic features that pointed towards Psoriatic Arthritis

The patient had psoriasis at locations that predict the development of Psoriatic Arthritis.

She also had intermittent early morning joint stiffness.

She had entheseal tenderness at one location that was not typical of Osteoarthritis i.e. the brim of the pelvis.

Her C-reactive protein was elevated.

Collectively these features would suggest Psoriatic Arthritis.

The features that pointed towards Osteoarthritis

However she also described constant joint pains that were more typical of Osteoarthritis.

She had clear evidence of Osteoarthritis on examination of her knees.

She was obese.

She had x-ray evidence for Osteoarthritis in her neck.

Collectively these features point towards Osteoarthritis.

Also patients with Osteoarthritis can get "inflammatory symtoms" with early morning stiffness and they may have an elevated CRP.

So the diagnosis would also be compatible with a type of Osteoarthritis known as "Inflammatory Osteoarthritis".

In reality specialists could argue about the final diagnosis. Some would suggest that there are actually 2 pathological processes taking place and that the patient has both Osteoarthritis and Psoriatic Arthritis.

How to treat such patients

Irrespective of the exact diagnosis the patient needs to lose weight and have some physiotherapy.

For obese patients in their 60th decade many specialists would seek to minimise the use of anti-inflammatory drugs or avoid them completely.

An intra muscular injection of corticosteroid may alleviate the stiffness irrespective of the exact diagnosis in this case.

In the absence of demonstrable joint swelling it is unlikely that this case has a propensity for progressive joint damage. However, vigilance and onging follow up is needed.

A trial of therapy with methotrexate or sulphasalasine or leflunomide may be suggested by some specialists. However, the evidence that such a strategy would work in this type of Psoriatic Arthritis or in inflammatory Osteoarthritis is lacking.

Without demonstrable swelling such patients would not be eligible for anti-TNF therapy in the United Kingdom.

However, we are aware of this strategy being used in other jurisdictions where funding costs are not an issue.

Take home messages

Some types of Osteoarthritis and Psoriatic Arthritis both cause disease at entheseal regions. This can make a clear cut diagnosis difficult.

Presently there is a lack of evidence to support the use of powerful anti-rheumatic drugs in this setting.

Depending on the severity of symptoms the treating Rheumatologist may go down this path.

Treatment can be continued if there is a good clinical response.

The role of Ultrasound and MRI in this setting remains controversial as these dont appear to reliably distinguish between Osteoarthritis and Psoriatic Arthritis.