[CUHK Medical Grand Rounds] Psoriatic arthritis: Clinical approach for measuring disease activity
Presentation, history and physical examination
A 27-year-old man with known psoriasis since the age of 23 years presented with intermittent pain and swelling over bilateral knees and the left ankle for 1 year. The symptoms were barely responsive to simple analgesics and non-steroidal anti-inflammatory drugs. The patient had one episode of visual disturbance in the form of blurred vision, eye redness and pain and sensitivity to light 1 year ago. The ocular symptoms resolved after using steroid eye drops prescribed by an ophthalmologist. The patient was not on follow-up for his psoriasis at any dermatology clinic.
This time, the patient attended the Accident and Emergency Department with severe left ankle swelling and pain, which made him unable to walk. On physical examination, the patient was found to be obese with a body mass index of 28 kg/m2. Active psoriatic plaques were found on his scalp, hairline, back and buttocks. (Figure 1) The majority of his fingernails showed pitting, ridging and onycholysis. (Figure 2) Both knees were mildly swollen. His left ankle was severely swollen over the lateral and posterior aspects, with tenderness upon palpation and movement. Dactylitis (“sausage digit”) was present on the left 5th toe. Localized tenderness was found over 3 out of the 13 specific enthesis upon palpation. These 3 tender enthesitic sites were the bilateral 1st costochondral joints and the left proximal insertion of the Achilles tendon. There was no spinal tenderness with passive and active ranges of spinal movement.
Clinical and laboratory investigations
Blood investigations showed mildly raised alanine transaminase. Complete blood count, renal function, albumin, bilirubin and alkaline phosphatase were all normal. Rheumatoid factor, anti-cyclic citrullinated peptide and human leucocyte antigen B27 (HLA-B27) were negative. C-reactive protein and erythrocyte sedimentation rate were elevated. The patient’s fasting glucose was 6.2 mmol/L and HbA1c was 5.6 percent. His lipid profile was normal. Hepatitis screen was negative.
The patient’s electrocardiogram was normal. X-ray of the knees and ankles were unremarkable. X-ray of the feet showed soft tissue swelling over the left 4th toe, with joint space preserved and no bone erosion. X-ray of the pelvis showed normal sacroiliac joint. Ultrasound of bilateral knees showed mild synovial hypertrophy with a small amount of effusion over both suprapatellar recesses. The fluid was aspirated and sent for culture and histology, with microbiological investigations being negative and histological examination showing no crystals or malignant cells. Ultrasound of the left ankle revealed hypoechoic enlargement of the peroneus longus and peroneus brevis tendons, with some anechoic distension of the tendon sheaths. (Figure 3) There was diffuse hypoechoic swelling and increased thickness over the left Achilles tendon, together with increased flow on power Doppler imaging. (Figure 4) Ultrasound of the abdomen showed mild fatty liver change.
Diagnosis and management
The patient was diagnosed as having psoriatic arthritis with peripheral arthritis, dactylitis, enthesitis and tenosynovitis of the peroneal tendons. There was associated obesity with impaired fasting glucose and mild fatty liver disease. His medical history was suggestive of a previous episode of uveitis. Methotrexate, a first-line disease modifying anti-rheumatic drug (DMARD) for psoriatic arthritis, was started with close monitoring of liver function. Steroid injection was given to both knees and the left peroneal tendon sheaths after joint infection had been ruled out. The pain and swelling quickly resolved, and the patient was able to walk the day after the injection. A physiotherapist had assessed his muscle strength and the range of movement of his lower limbs, and advised on techniques and exercises for rehabilitation of his mobility and general fitness. He was also seen by a dietitian for diet counselling. Upon discharge, early follow-up visits at both the rheumatology and dermatology clinics were arranged for proper management of his psoriasis and psoriatic arthritis. Biologic therapy may need to be considered for his enthesitis.
Psoriasis is among the most prevalent autoimmune diseases worldwide. Approximately 30 percent of patients with psoriasis will develop psoriatic arthritis, but 10.1–15.5 percent of patients with psoriatic arthritis were undiagnosed.1 Psoriatic arthritis is a heterogenous multifaceted inflammatory arthritis. In addition to peripheral arthritis, patients with psoriatic arthritis may also develop spondylitis, dactylitis, enthesitis, nail disease, as well as extra-articular features common to spondyloarthropathies. Based on these characteristics, psoriatic arthritis has been classified as one of the HLA-B27–associated spondyloarthropathies.
Because of the heterogeneous clinical manifestations of psoriatic arthritis, assessment of patients with the condition should cover all major disease domains, including peripheral arthritis, spondylitis, dactylitis, enthesitis, psoriasis and nail disease, to provide complete and reliable information about disease activity.2 Other related conditions and comorbidities, including obesity, metabolic syndrome, gout, diabetes, cardiovascular disease, liver disease, uveitis, inflammatory bowel disease, depression and anxiety, should also be assessed.
This case report highlights that psoriatic arthritis is a heterogenous disease affecting multiple disease domains, and effective treatment requires thorough assessment of each of these different domains. Very often, it is impossible to differentiate arthritis, enthesitis and tenosynovitis by clinical examination. As recommended by the European League Against Rheumatism (EULAR), different imaging modalities including X-ray, ultrasound and magnetic resonance imaging are required for the assessment and differentiation of these musculoskeletal manifestations.3The goal of therapy for psoriatic arthritis is to achieve the lowest possible level of disease activity in all domains of the disease.4 We aim to optimize patients’ functional status, improve their quality of life and well-being, and minimize structural damage to the greatest extent possible. Another aim is to avoid or minimize complications, both from untreated active disease and from therapy. A multidisciplinary team care approach should be adopted to provide the best care delivery for patients with this complex disease.