One size does not fit all

5 minute read

A case of psoriatic arthritis and psoriasis, complicated with comorbidities and lifestyle issues, shows the value of having a range of medications with differing modes of action.

A 53-year-old male presents for ongoing management of psoriasis and psoriatic arthritis.

He was diagnosed 15 years ago and managed on methotrexate monotherapy. He uses corticosteroid ointment for psoriasis flares, but his psoriatic arthritis has mostly been well controlled for many years.

Over the 6 months prior to presentation, he had recurrent pain and swelling to his ankles, mid feet and first MTP joint. Erythema was noted at the time of swelling, and he was unable to walk at times. The upper limbs were not affected.

Examination showed clear evidence of plaque psoriasis, nail disease and scalp psoriasis. CRP was raised at 13 (N<5) and ESR 45 (N<20). Serum uric acid was raised at 0.55 mmol/L. Liver function tests (GGT, ALT and AST) had been persistently abnormal for many years. He drank around 200g alcohol weekly.

The differential here is a flare of psoriatic arthritis or gout. Recurrent attacks in the lower limbs could be suggestive of gout. Gout is far less likely to affect the upper limbs, although it does occur in severe, prolonged disease and especially in tophaceous gout. It should also be noted that psoriatic arthritis occurs in roughly 30% of people with plaque psoriasis, 50% with scalp psoriasis and 80% with psoriatic nail disease.

Although there was some swelling at the time of examination, I did not feel there was enough to obtain a joint aspirate. A joint aspirate is the most reliable way to determine if a swollen joint is due to gout.

As a second line option, I elected for dual energy CT scans of both feet to look for urate crystals. This test is more reliable in long-standing disease or tophaceous gout. The sensitivity reduces significantly in early disease, such as the first or second episode of acute arthritis.

A small amount of urate crystals was identified in several joints of the midfoot and forefoot, so I felt that gout may be the likely cause of the recent increase in symptoms. I started allopurinol and titrated this until his serum uric acid was below 0.30 mmol/L. He required 400mg daily to achieve this. Colchicine was used as prophylaxis to prevent acute flares during the up-titration period.

His lower limb arthritis did improve for a few months, but 6 months later he presented with recurrent knee, ankle, wrist and MCP joint pain and swelling. ESR and CRP started to climb. I felt psoriatic arthritis was the likely cause given the new distribution of affected joints and adequate suppression of serum uric acid levels.

Management of his psoriatic arthritis was challenged by comorbidities. He had significant alcohol intake, he was obese (BMI 34) and there was a persistent abnormality of GGT, AST and ALT. Other tests showed impaired fasting glucose and high triglycerides, all features of metabolic syndrome.

He committed to reduce alcohol intake and addressed dietary factors with dietitian advice. Many studies have identified weight loss as effective interventions to reduce psoriasis and psoriatic arthritis disease severity. Ideally these non-pharmacological strategies should be utilised in all patients with psoriatic arthritis.

His disease activity remained high, and he required further treatment. Transaminases remained abnormal, so methotrexate was dose limited. Leflunomide can also increase transaminases, especially in combination with methotrexate. I elected to use sulfasalazine, but he had disabling headaches and nausea and could only continue for a few months.

His psoriatic arthritis remained active, and he was able qualify for PBS-subsidised biologic DMARD therapy. At the time, there was a limited range of biologic DMARDs available, and they were all TNF inhibitors. Adalimumab was chosen.

He had an initial good response, with reduction of ESR from 96 to 32 and CRP from 31 to 2, although there was only partial clearing of psoriasis. Liver function tests did improve with a vast reduction of alcohol intake and successful reduction of body weight. Methotrexate had to be ceased three years later due to worsening of transaminases. Unfortunately, this caused a significant worsening of both the psoriasis and psoriatic arthritis.

Fortunately, by this time a number of different biologic DMARDs were available on the PBS. He started ixekinumab (an IL-17 inhibitor). However, he had an urticarial skin reaction. He switched to secukinumab (another IL-17 inhibitor). However, this resulted in a variety of adverse reactions including widespread eczema and oral candidiasis. Candidiasis is reported at higher rates on people taking IL-17 inhibitors. Whilst this is not usually invasive and can be treated with usual therapies, it can significantly impact quality of life.

He was switched to ustekinumab, an IL-12/23 inhibitor. Whilst this was relatively slow to work, he had a fantastic response to this with virtual clearing of all plaque and scalp psoriasis and vast reduction of psoriatic arthritis disease activity.

There have been major advances in the knowledge of pathogenesis of psoriasis and psoriatic arthritis over the last two decades. This has translated into major therapeutic advances over the last decade.

Rheumatologists now have a variety of tools available to treat the wide range of manifestations of this disease (skin, nails, joints, enthesitis and dactylitis). There are still a number of agents in clinical trials, with JAK inhibitors and IL-23 inhibitors now listed on the PBS. Good results can now be achieved in most patients with psoriatic arthritis.

This case demonstrates the usefulness of having a range of medications with differing modes of action. There remain ongoing challenges treating this group of patients, where there are high rates of comorbidities such as obesity, metabolic syndrome and coexisting mental health disease. Treating obesity and other comorbidities will further improve outcomes.

Dr Andrew Jordan is a rheumatologist based in Parramatta, Sydney, with a special interest in inflammatory arthritis, gout and PRP injections.

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