Case 14: Scaly rash and joint pain
Tuesday, March 29th, 2011Author: Dr Sam Thenabadu
A 45 year old woman with a lifelong history of intermittent pruritic rashes, presents to the ED with swollen knees, wrists and MCPJs bilaterally. She has been bed bound for the last 3/52 and not been able to collect her prescription for methotrexate. She assures you that three weeks ago her joints were completely normal.
1. What is the diagnosis?
Click to see the answerThis is psoriatic arthropathy with the classic scaly rash of psoriasis and the obvious swelling of the joints. There are several manifestations of joint disease associated with psoriasis, so definitions vary, with differing diagnostic criteria. A common definition is an inflammatory arthritis associated with psoriasis, usually with a negative rheumatoid factor (RF) test known as a seronegative arthropathy.
Usually the rash precedes the arthritis by a few years, but the opposite is occasionally true. A family history of psoriasis may be the only clue to the aetiology of the arthritis in some cases. The condition can present in those with minimal or no obvious rash. Occult rash should be looked for on the scalp, on extensor aspects of the forearms/elbows, and in the umbilicus and natal cleft.
Enthesopathy affecting the Achilles tendon and plantar fascia is frequently seen.
2. How is the disease mediated?
Click to see the answerThe disease is autoimmune-mediated with defined HLA associations (HLA-B27). Occasionally, it may occur in the absence of skin disease, or there may only be an insignificant rash which may not be noticed by the sufferer.
3. This process often affects the nails. Name the classic changes and some other conditions that can cause these changes?
Click to see the answerMore than 80% of patients with psoriatic arthritis will have psoriatic nail lesions characterised by pitting of the nails, or more extremely, loss of the nail itself (onycholysis). Other causes of pitting include :
- Reiter’s syndrome and in other connective tissue disorders
- sarcoidosis
- pemphigus
- alopecia areata
4. What are the common treatment options for this condition?
Click to see the answerMethotrexate, retinoids and PUVA appear most effective at treating skin and joints together. Other options include:
- Non-steroidal anti-inflammatory drugs (NSAIDs) – but can worsen skin condition, in which case try a different agent or class of NSAID. Indometacin is often used due to its potency but has significant gastrointestinal and renal side-effects.
- Intra-articular steroids are useful and may be used to inject periarticular structures for enthesopathy.
- Disease-modifying antirheumatic drugs (DMARDs) should be used in patients with persistent inflammation, under expert guidance. Oral methotrexate and sulfasalazine have been shown to be effective and safe on the basis of systematic reviews.
- Drugs that modify the effect of tumour necrosis factor alpha (TNF-alpha), e.g. soluble fusion proteins like etanercept or monoclonal antibodies such as infliximab, are under evaluation for this particular indication.