Introduction

Ankylosing spondylitis is the commonest spondyloathropathy and is covered in detail in Chapter 25. Psoriatic, reactive and enteropathic arthritis are also referred to as spondyloarthropathies if they involve inflammatory spinal pain at some course during their natural history.

Psoriatic arthritis

Five to ten percent of patients with psoriasis develop arthritis. The male: female ratio is equivalent, with a peak incidence between 20 and 40 years of age. Clinical patterns vary widely including:

Distal hand disease predominantly affecting the distal interphalangeal (DIP) joints.
Symmetrical polyarthritis similar to rheumatoid arthritis.
Spondyloarthropathy.
Asymmetrical oligoarthritis.
Arthritis mutilans due to osteolysis of the small joints in the hand.

Dactylitis (so-called ‘sausage finger’), tenosynovitis and enthesitis are also common.

Diagnosis

Differentiating rheumatoid arthritis (RA) in a patient with coexistent psoriasis from true psoriatic arthritis (PsA) can be difficult, especially since up to 10% of those with PsA are rheumatoid factor positive. ACPA (anti-CCP) antibodies are generally absent however. Clinically, the presence of disease at the DIP joint and/or psoriatic nail changes such as pitting, ridging, onycholysis, and salmon-pink patches would suggest an underlying diagnosis of PsA rather than RA. Radiological indicators of a diagnosis of PsA rather than RA include:

Absence of juxta-articular osteopaenia.
Whittling of the terminal phalanges (acro-osteolysis).
Pencil-in-cup deformity (erosion of the proximal and expansion of the distal portion of an interphalangeal joint).
Ankylosis.

Since psoriasis is a high cell turnover state, hyperuricaemia and gout are also possible causes for arthropathy in this population.

Treatment

NSAIDs and occasional intra-articular steroid injection can be used as a ‘rescue’.
Methotrexate and/or leflunomide (may also improve skin).
Sulfasalazine, azathioprine, penicillamine, gold and cyclosporin in severe cases.
Avoid use of hydroxychloroquine as it may produce flares of skin disease.
Biologic therapy in the form of anti-TNFα for those with refractory joint disease (≥3 tender and ≥3 swollen joints despite trials of at least two DMARDs) is very effective.

Reactive arthritis/Reiter’s syndrome

Any of the spondyloarthropathies are considered ‘reactive’ if a history of urethritis/cervicitis or diarrhoea is present. Urethritis is commonly due to Chlamydia and may be asymptomatic; the diarrhoeal illness has usually occurred within the preceding month and the most likely pathogens are Shigella, Salmonella and Campylobacter. The syndrome may develop acutely with fever, weight loss and polyarticular involvement, but more commonly patients present with a mono- or oligoarthritis and either a low grade or absent fever.

Additional features that may be present include:

Painless ulcers on the palate.
Balanitis circinata: painless plaques on the glans or shaft of the penis.
Keratoderma blennorrhagica: a painless papular/pustular rash on the palms or soles of the feet.
Conjunctivitis: may be followed by uveitis.
Enthesitis.

Recurrent/repeated infections do not always lead to recurrence of arthritis. Other post-infective arthropathy differentials include HIV, Lyme disease, Behget’s disease and parvovirus.

Diagnosis

The diagnosis relies on a careful history/examination and the combination of raised inflammatory markers, as well as the results of serologic testing, cultures and swabs. Joint aspirate will rule out a septic or crystal arthropathy. There are no classic radiological features. HLA-B27 is not helpful with diagnosis but B27+ve patients tend to have a more prolonged, severe course to their arthritis.

Treatment

NSAIDs and local corticosteroid injections will suffice for many patients, and the majority are in remission within 2 years. However, persistent disease (particularly a problem in B27+ve patients) may require DMARDs such as sulfasalazine.

Antibiotic therapy against the precipitating infection may not have any impact on the arthropathy.

Enteric arthropathy

Up to 20% of patients with either Crohn’s disease or ulcerative colitis develop an arthropathy. Of those with arthritis, two-thirds have peripheral symptoms and one third develop AS-like disease.