subtype, shows a severe destructive and deforming polyarthritis with ankylosing of joints, ÒtelescopingÓ of digits, and possible ankylosis of the spine. Apart from this deforming group, PA is not a severe disease; the pain and disability are much less than those produced by RA [265].

6.1.5.3 Ocular Manifestations

Eye lesions of psoriasis consist of conjunctivitis and anterior uveitis and occasionally scleritis and episcleritis [266]. Anterior uveitis is usually mild with Þne endothelial keratic precipitates. PA must always be considered in the differential diagnosis of anterior uveitis.

Scleritis

The reported incidence of PA in patients with scleritis is 1.44% [122]. Conversely, the reported incidence of scleritis in patients with PA is 1.8% [266]. Scleritis in PA usually appears after many years of active disease and, although diffuse anterior scleritis is often seen [204], it may take almost any form of scleritis.

In our own series of 500 patients with scleritis, Þve patients had PA (1%). They were three females and two males with a mean age of 54 years. Three patients had diffuse scleritis and two patients had posterior scleritis with choroidal folds, subretinal mass, choroidal detachment, and diffuse anterior scleritis. All patients had had PA for many years. One patient had anterior uveitisassociated scleritis (sclerouveitis) and two patients had previous episodes of recurrent anterior uveitis. There was no conjunctivitis, glaucoma, cataract, or macular edema, and Þnal visual acuity was not decreased. Any patient who develops scleritis should be questioned and examined for skin and nail lesions. Any patient who develops scleritis after previous episodes of recurrent anterior uveitis should be examined for PA, ReA, or AS.

Episcleritis

Episcleritis is also uncommon in PA and usually occurs after years of active disease. In our own series of 85 patients with episcleritis, one patient had PA (1.2%). The patient was a 48-year-old female with chronic seronegative asymmetric oligoarthritis and skin psoriatic lesions, especially in

legs and scalp. Unilateral simple episcleritis appeared 5 years after the onset of the psoriasis and recurred many times. There were no other ocular Þndings or decrease in visual acuity.

6.1.5.4 Laboratory and Radiographic Findings

Tests for rheumatoid factor and ANAs are usually negative. The ESR is frequently elevated and mild anemia may appear. Hyperuricemia may be associated in patients with severe skin involvement and gout has been reported on several occasions [267]. HLA-B27 is found in 50Ð70% of patients with axial disease, but in less than 15Ð20% in patients with only peripheral joint involvement.

Radiographic Þndings depend on the type of articular involvement. Distal interphalangeal joints may show erosions with widening of the joint space and expansion of base of terminal phalanx. Dissolution of bones, especially the metatarsal, may be seen in Òarthritis mutilansÓ resulting in a Òpencil in cupÓ appearance or ÒÞsh tailÓ deformity. Characteristics of axial PsA include asymmetric sacroiliitis; compared with idiopathic AS, less zygoapophyseal joint arthritis and fewer and less symmetric and delicate syndesmophytes; ßuffy hyperperiostosis on anterior vertebral bodies; severe cervical spine involvement, with a tendency to atlantoaxial subluxation but relative sparing of the thoracolumbar spine; and paravertebral ossiÞcation [261]. Ultrasound and MRI both readily demonstrate enthesitis and tendon sheath effusions that can be difÞcult to assess in physical examination.

6.1.5.5 Diagnosis

Psoriatic arthritis is diagnosed in the presence of skin psoriatic lesions and the presence of one or more swollen joints for at least 3 months (elbows, wrists, knees, ankles, metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints of the hands and feet, sacroiliacs, lumbar or cervical spine), with radiologic changes compatible with PA, including erosions in peripheral joints or deÞnite spinal changes. As in AS or ReA, the Þnding of HLA-B27 positivity increases the probability that the presumptive diagnosis is