Differential diagnosis
Several conditions can mimic the clinical presentation of psoriatic arthritis including rheumatoid arthritis, osteoarthritis, reactive arthritis, gouty arthritis, systemic lupus erythematosus, and inflammatory bowel disease-associated arthritis. In contrast to psoriatic arthritis, rheumatoid arthritis tends to affect the proximal joints (e.g., the metacarpophalangeal joints), involves a greater number of joints than psoriatic arthritis, and affect them symmetrically. Involvement of the spinal joints is more suggestive of psoriatic arthritis than rheumatoid arthritis. Osteoarthritis shares certain clinical features with psoriatic arthritis such as its tendency to affect multiple distal joints in an asymmetric pattern. Unlike psoriatic arthritis, osteoarthritis does not typically involve inflammation of the sacroiliac joint. Psoriatic arthritis sometimes affects only one joint and is sometimes confused for gout or pseudogout when this happens. Classification
There are five main types of psoriatic arthritis:
Oligoarticular: This type affects around 70% of patients and is generally mild. This type does not occur in the same joints on both sides of the body and usually only involves fewer than 3 joints. Polyarticular: This type accounts for around 25% of cases, and affects five or more joints on both sides of the body simultaneously. This type is most similar to rheumatoid arthritis and is disabling in around 50% of all cases. Arthritis mutilans (M07.1): Affects less than 5% of patients and is a severe, deforming and destructive arthritis. This condition can progress over months or years causing severe joint damage. Arthritis mutilans has also been called chronic absorptive arthritis, and may be seen in rheumatoid arthritis as well.
Macrophage activation syndrome (MAS) is a known, life-threatening disorder that may develop in people with rheumatic conditions, in particular Stills disease, and should be aggressively treated. Treatment with immunosuppressants may increase the risk of malignancies. People are advised not to receive live vaccinations during treatment. History
Canakinumab was being developed by Novartis for the treatment of rheumatoid arthritis, but this trial was completed in October 2009. Canakinumab is also in phase I clinical trials as a possible treatment for chronic obstructive pulmonary disease, gout, and coronary artery disease (the CANTOS trial). It is also in trials for schizophrenia. In gout, it may result in better outcomes than a low dose of a steroid, but costs five thousand times more. One 150 mg subcutaneous injection, usually needed every two weeks, costs over $16,700.On 27 August 2017, the results of the CANTOS trial were announced at the European Society of Cardiology and published in The Lancet and The New England Journal of Medicine. Those treated in CANTOS had a 15% reduction in deaths from heart attacks, stroke and cardiovascular disease combined. However, there were serious side-effects and no statistically significant overall survival benefit. Although the CANTOS study says, "Overall, canakinumab was tolerated well with essentially identical discontinuation rates compared to placebo. Mild neutropenia and thrombocytopenia were slightly more common in those treated with canakinumab. Rates of death due to infection or sepsis were low but more likely in the canakinumab group compared to placebo (incidence rate 0.31 vs. 0.18 per 100 person-years, P = 0.02).