Psoriasis and Arthritis

The literature on this subject shows considerable divergence of opinion on the significance of the association of psoriasis and erosive arthritis, and on what may be said to comprise "psoriatic arthropathy", if the term is to be used at all. The difficulties of the problem are increased by the fact that according to the predominant complaint the patient may fall into the hands of either the rheumatologist or the dermatologist, and escape the statistical eye of one or the other. The difficulty in assessing the incidence is indicated by the diverse figures given in the literature-an aspect recently reviewed by Gribble (1955). Among dermatologists, however, it is generally agreed that atrophic arthritis is commoner among patients with psoriasis (Leczinsky, 1948: 5 8 per cent. males, 7 9 per cent. females; Ingram, 1954: 7 per cent.) than among the general population. Among rheumatologists it is agreed by the majority that psoriasis occurs in about 3 per cent. of patients with atrophic arthritis (Dawson and Tyson, 1937; Bauer, 1939) as compared with 0 7 per cent. in the general population (Ingram, 1954), while there is no significant increase in the incidence among patients with osteo-arthritis. Many workers have endeavoured to define an entity "psoriatic arthropathy", and the following definitions have been suggested: (I) A form of atrophic arthritis associated with psoriasis and exhibiting a reasonable degree of synchronous activity as evidenced by remissions and relapses in arthritis and cutaneous manifestations (Lane and Crawford, 1937; Jeghers and Robinson, 1937; Epstein, 1939). (2) Arthritis restricted to the distal interphalangeal joints associated with psoriasis (Bauer, Bennett, and Zeller, 1941). (3) A syndrome in which both skin lesions and arthritic manifestations are atypical (Dawson, 1937), or in which the joints are improved by treatment of the skin (O'Leary, 1943). (4) A peculiarly destructive form of arthritis associated with psoriasis (Fawcitt, 1950).