Internal Diseases and Therapy · MU Sofia

43. Psoriatic arthritis

Covers psoriatic arthritis as a seronegative spondyloarthropathy linked to psoriasis, noting its prevalence, lack of correlation with skin extent, risk factors, and the nail changes that help identify it. It describes HLA associations, the synovitis histopathology that distinguishes it from rheumatoid arthritis, and possible joint damage if untreated. A five-pattern classification with approximate frequencies is set out, followed by a brief treatment outline using NSAIDs and second-line DMARDs.

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Topic 43 of 139 in the MU Sofia syllabus for Internal Diseases and Therapy (Medicine, Years 4 and 5). The free AceMed note covers it in 1 section, about 348 words (2 min of reading), with 15 flashcards.

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  1. Psoriatic arthritis

Psoriatic arthritis

Psoriasis is an autoimmune disease characterised by red scaly patches, psoriatic arthritis refers to a type of arteritis associated with psoriasis. It is another one of our seronegative spondyloarthropathies. It develops in about 5% of patients with psoriasis, but there is no real correlation between the extent of the psoriasis and joint involvement. The riks for psoriatic arteritis increases with FH of spondyloarthritis. Some cases of psoriatic arthritis will occur prior to or without skin involvement, so this should be considered when performing physical examination. Around 80% of patients have nail changes, so called Onycholysis and nail pitting, so careful assessment of the hands is vital.

Image: “Luszczyca paznokcia” by Seenms, CC BY-SA 3.0, via Wikimedia Commons.

Psoriatic arthritis more commonly affects males, and onset is usually between 30-55 years of age, with obesity being a major risk factor in the disease. Psoriasis (and by extension psoriatic arteritis) is associated with several HLA loci, specifically HLA cw6, HLAB39 and HLA b27. There is no proven etiological agent, and the histopathology of the synovitis of psoriatic arthritis is the same as other forms of spondyloarthritis with an absence of local production of immunoglobulin and rheumatoid factor, differentiating the disease from RA. Within the joints the immune cells activate osteoblasts and osteoclasts (much like they activate keratinocytes and fibroblasts in the skin) which go on to form joint deformity.

Psoriatic arthritis if untreated can cause osteolysis, fibrous ankylosis, and heterotopic bone formation to occur.

There are five patterns of psoriatic arthritis:

  • Asymmetrical oligoarthritis (40%) - presents insidiously, usually involving hands and feet, there is a combination of synovitis and periarticular changes
  • Symmetrical polyarthritis (20%) - more common in females, similar to RA but nodules and extra-articular features are absent (aka Rheumatoid pattern)
  • Psoriatic spondylitis (20%) - similar presentation to ankylosing spondylitis
  • Distal IPJ arteritis (15%) - more common in males, DIPJ form associated with nail dystrophy
  • Arthritis mutilans (5%) - erosive arthritis usually involving digits, characterised by cartilage and bone destruction

NSAIDs are usually sufficient for treatment of the disease, DMARDs can be added as a second line if required.

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