Psoriatic Arthritis-Laboratory Findings, Diagnosis and Treatment

In Psoriatic arthritis, there are few laboratory abnormalities. Elevated erythrocyte sedimentation rates, C-reactive proteins and complement levels reflect inflammation. Rheumatoid factors are uncommon and are more likely to be observed in those with symmetric arthritis. Immunoglobulin levels, especially IgA levels, may be elevated.

Uric acid levels may be elevated; sodium urate crystals in joint fluids suggest gout.

Radiologic investigation reveals findings similar to those of rheumatoid arthritis, soft tissue swelling, loss of the cartilage space, erosions, bony ankylosis of fingers, subluxations, and subchondral cysts. There is less demineralization.

Following features if present are suggestive of psoriatic arthritis

• Erosions at DIP joints
• Expansions and cuplike erosions of and bony proliferation of the distal terminal phalanx
• Proliferation of bone near osseoperiostitis, and telescoping of one bone into its neighbor

The axial skeleton shows asymmetric or unilateral sacroiliitis, often asymptomatic paraverterbal ossification, including cervical involvement, and large asymmetric no marginal syndesmophytes.

Psoriatic arthritis is suspected if a person with psoriasis presents with arthritis. Psoriasis should be distinguished from seborrheic dermatitis and eczema.

Psoriatic lesions may be quite small peripherally and often are hidden in the scalp, umbilicus, and gluteal folds.

Fungal infection of nails can be distinguished from psoriasis by pitting and onycholysis.

It is often difficult to distinguish Reiter’s syndrome from psoriatic arthritis, since both manifest with dactylitis.

Reiter’s syndrome usually presents in younger individuals, especially mails, is less frequently progressive or destructive and is more likely to be associated with characteristic skin lesions (keratoderma blenorrhagica), urethritis, and conjunctivitis.

Gout can be distinguished by the presence of intraarticualr sodium urate crystals.

Psoriatic arthritis is distinguished from rheumatoid arthritis by the relative lack of rheumatoid factors, the tendency to asymmetry, dactylitis, iritis, enthesopathy, and onychondystrophy, the high frequency of HLA-B27, especially in patients with axial skeletal involvement, and characteristic radiologic features.

Treatment

NSAIDS are mainstay of the traetment to reduce inflammationand symptoms.

Orthotics and intrarticular injections are to be given as and when required.

Patient education and physiotherapy are very important parts of the treatment.

In patients with more severe involvement, a disease-modifying antirheumatic drug should be used. Drugs used are

• Methotrexate – For more severe cases, especially with extensive skin involvement, 5 to 25 mg methotrexate per week is recommended. Folic acid is recommended alongwith to prevent hematologic complications.Renal and liver function tests and complete blood count should be performed frequently
• Hydroxychloroquine- Successful in producing either amelioration or remission but carries a significant risk of exacerbation of psoriasis and exfoliation.
• Sulfasalazine
• Cyclosporine
• Etretinate
• 6-mercaptopurine
• Azathioprine have also proved successful.