What is Inflammatory Polyarthritis?
The term inflammatory polyarthritis (IPA) relates to a family of diseases, where immune system dysfunction causes inflammation within joint tissues such as the synovial membrane or joint entheses (where tendons or ligaments join bone). This inflammation causes pain and swelling; in some diseases, without treatment, this can result in damage to cartilage and bone which is irreversible. This contrasts with osteoarthritis, where multiple factors such as age, biomechanics, and genetics combine to effect articular cartilage loss.
Inflammation within the polyarthritis family is not just confined within the joints and soft tissues; symptoms such as fatigue are common, as are symptoms outside of the joints. The diseases can occur at any age, and affect both males and females.
Rheumatoid arthritis, spondyloarthritis and psoriatic arthritis are the commonest forms of IPA. Other autoimmune conditions such as systemic lupus erythematosus, juvenile inflammatory arthritis, and other forms of connective tissue disease and vasculitis can cause joint inflammation.
Diagnosing these diseases early prior to damage occurring is crucial; inflammation caused by inflammatory arthritis is reversible, whilst joint damage is not.
What is Rheumatoid Arthritis?
Rheumatoid Arthritis (RA) is the commonest form of auto-immune inflammatory polyarthritis; there are approximately 400,000 people with RA in the UK. RA has a peak age of incidence of 70, though the disease can occur at any age.
RA causes chronic inflammation of the joint synovial membrane, classically causing symmetrical symptoms and swelling in the small joints of the hands and feet, alongside larger joints. If not controlled, synovial inflammation can lead to erosion of cartilage and bone, causing joint damage and deformity.
Alongside joint disease, systemic symptoms such as fatigue, weight loss & fever are common, and can predate joint symptoms by several months.
What is Spondyloarthritis?
What is Psoriatic Arthritis?
Psoriatic arthritis (PsA) is an arthritis associated with skin psoriasis. Confusingly, patients do not have to have skin psoriasis to be given the diagnosis; 20-30% of patients with PsA will not have active skin psoriasis, though will usually have a personal or family history of psoriasis of the skin or nails.
The prevalence of psoriatic arthritis is thought to be around 0.1-0.3%. Around 10% of all people with psoriasis have PsA. PsA affects men & women equally, with peak incidence of between 30-55 years.
The major clinical difference between PsA and RA is distribution; PsA is more likely to be asymmetrical, and more likely to involve distal interphalangeal joints, large joints, or the spine. Psoriatic arthritis is also much more likely to cause inflammation at entheses (where tendons or ligaments join to bone), or dactylitis, where a whole digit is swollen & tender. As with RA, PsA commonly causes systemic symptoms such as fatigue.
What about Crystal Arthritis?
Gout, and other forms of crystal arthritis, are important differentials to consider when assessing patients with joint inflammation.
Diagnosis and management of crystal arthritis falls beyond the remit of this toolkit. The follow resources offer further information and advice: