Two cases of distal extremity swelling with pitting oedema in psoriatic arthritis: the different pathological mechanisms.

In psoriatic arthritis, swelling and pitting oedema may be caused by different pathogenic mechanisms: on one hand, the involvement of tenosynovial structures; on the other hand, the involvement of lymphatic vessels, which may be rarely implicated by the inflammatory process. This different involvement is responsible for a different response to therapy and a different clinical outcome. In fact, patients with inflammation of the tenosynovial structures and normal lymphatic drainage have a more favourable clinical outcome and response to pharmacologic treatment, whilst patients affected by psoriatic arthritis with chronic lymphatic vascular damage are characterized usually by resistance of oedema to therapy. In this study, we report two cases of psoriatic arthritis with distal extremity swelling and pitting oedema. In the first patient, the swelling and pitting oedema were associated with lymphatic obstruction, as detected by lymphoscintigraphy. In the second, the predominant involvement of the tenosynovial structures, as shown by magnetic resonance, with normal lymphatic flow, may have been the cause of arthritis with oedema. These different pathogenetic mechanisms were associated with different response to therapy. Nevertheless, oedema was resistant to therapy in both patients probably because of other unknown factors, which influence therapy and clinical outcome.