Is the involvement of the distal interphalangeal joint in psoriatic patients related to nail psoriasis?

The aim of this study was to investigate the relationship between onychopathy and distal interphalangeal (DIP) joint involvement in psoriatic patients. Twenty-five consecutive unselected, unrelated patients with psoriatic onychopathy and 25 consecutive unselected, unrelated patients with psoriatic arthritis without onychopathy, were enrolled in the study. X-ray films of the hands were taken to identify DIP arthritic involvement and/or bone changes of the distal phalanx, which were categorized into five classes (0: no lesions; 1: tuftal minimal erosions; 2: tuftal bone resorption; 3: tuftal periosteal osteitis; 4: overlap of erosive and osteitic changes). Ten psoriatic patients with onychopathy and 8 without showed DIP arthritis, with no statistical differences in this distribution ( p=0.556). Bone changes of the distal phalanx were found in all 25 psoriatic patients with onychopathy and in 18 without. The distribution of patients in different categories of involvement of the distal phalanx showed that patients without onychopathy were markedly distributed in the categories with no or minimal lesions, whereas patients with onychopathy had structural changes prevailing included in categories with more severe bone changes (osteitis and overlap of erosive and osteitic changes) ( p=0.002). Onychopathic patients with DIP arthritis were older than those without ( p<0.0001) and showed a longer duration of onychopathy ( p<0.0001). Although the occurrence of DIP arthritis seems to depend on the duration of nail involvement, no statistical difference has been found in the distribution of DIP arthritis in psoriatic patients with or without onychopathy. In contrast, a topographical association between bone changes of the distal phalanx and dystrophy of the adjacent nail may be advanced.