Psoriatic Arthritis¶

Tina Arkee

Background¶

Men and women are equally affected, average of onset 30-50, and may have a family history of psoriasis
Up to 30% of patients with psoriasis develop arthritis at some point in their disease course
Psoriasis precedes the development of arthritis in most cases
Patients may experience trauma to the affected joint prior to development of arthritis (Koebner phenomenon)
Multigenic autoimmune disease that involves inflammatory infiltrate (likely drive by CD8 T cells) to entheses, synovial tissue, and skin
Classified under seronegative arthritis, though up to 15% of patients will have serologic positivity (RF most common)

Multiple patterns of joint involvement: DIP arthritis (most common), asymmetric oligoarthritis (large joint involvement in addition to small joints), symmetric polyarthritis (may look like RA), axial arthritis (involves the spine and SI joints), arthritis mutilans (severe destructive joint disease leading to osteolysis and shortening of digits)
Enthesitis: inflammation of tendon and ligament insertion sites, including the Achilles tendon, patellar tendon, and spinous processes of vertebral bodies
Tenosynovitis: flexor tendons of hands and posterior tibial tendons often involved
Dactylitis: diffuse swelling of a single finger or toe (sausage digit). Acute dactylitis presents with a red, hot, tender, swollen digit, whereas chronically affected digits are often just swollen.
Extra-articular manifestations: nail changes (pitting, ridging, onycholysis), psoriasis plaque, chronic bilateral uveitis, conjunctivitis
Comorbidities: Decreased bone mineral density, psychiatric disease (depression, anxiety), hyperuricemia, increased risk of CVD/metabolic syndrome/DM/fatty liver

Laboratory data: CBC, BMP, uric acid, ESR, CRP, could consider HIV testing
- Autoimmune testing to rule out other conditions: ANA (shouldn’t have high titer positivity), RF (positive in 2-10%), anti-CCP
- HLA-B27: present in 25-30% patients; may be helpful as one of the genetic markers that identifies patients at risk for axial disease or acute anterior uveitis
Imaging
- X-rays often show evidence of both bone erosion and new bone formation, such as the “pencil in cup” deformity (often involves the DIP), osteolysis leading to digital shortening, bone spurs at entheses, periosteal reactions (new bone formation around eroded sites), and ankylosis (fusion of adjacent joints).
- MRI changes can be more sensitive in detecting articular and soft tissue inflammation and sacroiliitis; however, these do not always correlate with clinical symptoms
CASPAR criteria for diagnosis are >90% sensitive and specific for PsA. Need 3 out of 5 to meet diagnostic criteria
- Current psoriasis, a personal history of psoriasis, or family history of psoriasis
- Psoriatic nail findings observed on physical exam
- Negative test for RF
- Current dactylitis or a history of dactylitis documented by a rheumatologist
- Xray evidence of juxta-articular new bone formation in the affected hand or foot

Peripheral arthritis or dactylitis: choice depends on severity of disease
- Mild arthritis: NSAIDs (e.g. naproxen 375-500mg BID)
- Moderate or resistant to NSAIDs: conventional DMARDS like MTX 15-25mg q weekly or LEF 20mg QD, occasionally apremilast (PDE4 inhibitor) if avoiding biologics
- Severe (many joints, erosive, functional limitation) or no response to above: biologic DMARD usually TNF inhibitor (infliximab, adalimumab, etanercept); if no response, trial to another TNF inhibitor before next step. If TNFi are contraindicated OR psoriasis is severe, try an anti-IL17a biologic (secukinumab, ixekizumab). Patients with concomitant IBD may benefit from anti-IL12/IL-23 agents (ustekizumab). Anti-IL17 biologics are contraindicated in patients w/IBD.
- Refractory to two TNFi/IL-12/IL-23: consider the JAK inhibitor tofacitinib
Avoid oral glucocorticoids given risk of developing erythroderma or pustular psoriasis
Nonpharmacologic: PT/OT, exercise, weight loss, nutritionist referral for metabolic syndrome