ARTHRITIS, PSORIATIC

ARTHRITIS, PSORIATIC - Michael Tutt, MD; Jeremy Golding, MD
BASICS
DESCRIPTION
Arthritis associated with psoriasis. Serologic tests for rheumatoid factor usually are negative. Patients exhibit sausage-shaped digits and characteristic radiologic changes. Psoriatic arthropathy occurs in ~5% of individuals with psoriasis, especially those with psoriatic nail disease. Several forms have been described, although separation into these forms is not distinct. Different authors call them by different descriptive terms.
• Forms of psoriatic arthropathy
- Psoriatic nail disease and distal interphalangeal involvement (classic psoriatic arthritis). Characteristics
 Nail pitting
 Transverse depressions
 Subungual hyperkeratosis
 Distal interphalangeal arthritis
• Arthritis mutilans: Destructive, resorptive arthropathy; produces so-called opera-glass hand
• Symmetric polyarthropathy resembling rheumatoid arthritis (RA): May be indistinguishable from RA, and may be coincidental RA in a patient who has psoriasis
• Asymmetric oligoarthropathy (more common type): Little relationship between joint and skin activity; joints involved may be both large and small
• Psoriatic spondylitis: Asymmetrical spondylitis and sacroiliitis
• System(s) Affected: Musculoskeletal; Skin/exocrine, Visual
• Synonym(s): Psoriasis, arthropathic
EPIDEMIOLOGY
• Typical onset age 30-35
• Not commonly seen in pediatric population
• Predominant sex: Female > Male (slightly)
Prevalence
• Prevalence 1-2 individuals per 1000 population.
• 5-20% of individuals with psoriasis will develop joint disease.
RISK FACTORS
• Psoriasis
• Positive family history
Genetics
• HLA-B27 usually present in patients with spondylitis-type psoriatic arthropathy
• Psoriasis itself is associated with HLA-B13, HLA-Bw17, HLA-Cw6, HLA-Bw38, HLA-DR4, and HLA-DR7.
ETIOLOGY
• Unknown
• Probably genetically related
• Pathogenesis: In contrast to ameliorating affect of AIDS (HIV infection) on RA, AIDS is associated with more aggressive joint disease in psoriatic arthritis. Theoretically, then, CD4 cells, which seem to "drive" RA, are not involved in pathogenesis of psoriatic arthritis.
ASSOCIATED CONDITIONS
Psoriasis


DIAGNOSIS
SIGNS AND SYMPTOMS
• Joint swelling, tenderness, warmth, restricted movement
• Dactylitis
• Distribution of arthritis depends on form of psoriatic arthritis
• Nail changes
- Pitting
- Transverse ridging
- Onycholysis
- Keratosis
- Yellowing
- Destruction of entire nail
• Fever
• Malaise
• Psoriasis: Variable severity
• Arthritic symptoms are worse in geriatric population.
• Some individuals develop uveitis.
TESTS
Lab
• Serum rheumatoid factor: Negative
• Elevated ESR
• Elevated uric acid
• Anemia
• HLA B27 (if spondylitis)
Imaging
• Radiographs
- Gross destructive changes of isolated small joints
- Peripheral arthritis mutilans
- Erosions, ankylosis
- Extensive bone resorption to cause opera-glass hand
- Fluffy periostitis
- Atypical spondylitis with syndesmophyte formation
- Acro-osteolysis, "pencil-in-cup" appearance
- Asymmetric sacroiliitis
- Absence of osteoporosis
• MRI is sensitive in detecting sacroiliitis, joint synovitis, erosions, and enthesitis.
Pathological Findings
Synovitis (resembling RA)
DIFFERENTIAL DIAGNOSIS
• Psoriasis
• Seropositive inflammatory polyarthritis
• RA
• Osteoarthritis
• Gout
• Reiter syndrome
• Ankylosing spondylitis
TREATMENT
GENERAL MEASURES
Outpatient
• Immobilizing splints
• Isometric exercises and swimming later
• Paraffin baths or other heat therapy
• Protection of affected joints
• Regular, moderate exposure to sun
• Psoriatic skin care
Diet
No special diet
Activity
Encourage exercise (particularly swimming) to maintain strength and flexibility.
MEDICATION (DRUGS)
First Line
• Several options available, depending on involvement of skin and joints
- NSAIDs in usual doses; no evidence for superiority of any one NSAID. NSAIDs are usually 1st-line treatment.
- Local corticosteroid injection
- Low-dose systemic steroids, if necessary
- Topical therapy including steroids for skin
- PUVA therapy may be helpful for skin lesions
• Disease-modifying agents may be useful if disease remains active despite use of NSAIDs, and should be introduced early if aggressive, deforming, or erosive disease is present:
- Methotrexate, for severe or extensive disease may be effective
- Leflunomide
- Gold salts
- Antimalarials (controversial)
- Sulfasalazine
- Immunosuppressives in resistant cases
- Cyclosporine (Neoral) in resistant cases
- Combination of methotrexate and cyclosporine or sulfasalazine under guidance of rheumatologist
• Contraindications
- NSAIDs may flare psoriasis.
- Methotrexate is contraindicated in HIV-positive patients.
• Precautions
- Phenylbutazone may cause bone-marrow depression.
- NSAIDs and aspirin may cause gastritis and renal failure.
- Refer to manufacturer's literature.
• Significant possible interactions: NSAIDs may impair methotrexate excretion and cause methotrexate toxicity. Refer to manufacturer's literature.
Second Line
Etretinate 0.5-1.0 mg/kg/d in 2 divided doses
ALERT
Pregnancy Considerations
Avoid medications (e.g., methotrexate, gold, antimalarials, sulfasalazine, cyclosporine, etretinate) during pregnancy.
FOLLOW-UP
PROGNOSIS
• Course: acute, intermittent
• More favorable than for RA (except for 20% of patients who develop arthritis mutilans)
• Treatment of skin lesions can sometime improve arthritic symptoms.
• Joint surgery is at least as successful as for RA; infectious complications are more common.
COMPLICATIONS
• Chronicity
• Severe deforming arthritis (arthritis mutilans)
• Spondylitic form of arthritis with sacroiliitis and spinal involvement
• Corticosteroids may destabilize psoriatic lesions.
• Antimalarials can provoke exfoliative dermatitis.
PATIENT MONITORING
Frequent follow-up for medication adjustment and encouragement
REFERENCES
1. Gladman D. Psoriatic arthritis. Up To Date 2006.
2. Kelley WN, Harris ED, Ruddy S, et al. Textbook of Rheumatology, 5th ed. Philadelphia: WB Saunders, 1997.
3. Kippel JH, Dippe PA, eds. Rheumatology. St. Louis: Mosby, 1994.
4. Koopman WJ, ed. Arthritis and Allied Disorders, 13th ed. Philadelphia: Lea  Febiger, 1997.
5. Salvariniet et al. Psoriatic arthritis. Curr Opin Rheumatol. 1998;10:299-305.