BACKGROUND: Ustekinumab has been most recently approved for psoriasis treatment and its efficacy on nail psoriasis is still underreported.METHODS: Twenty-seven patients suffering from moderate-to-severe plaque psoriasis with nail involvement were enrolled in this open-label, uncontrolled, nonrandomized study to evaluate the therapeutic potential of ustekinumab. Participants were scheduled to receive subcutaneous injections of ustekinumab at a dose of 45 mg at baseline and week 4 and every 12 weeks thereafter. Nail Psoriasis Severity Index (NAPSI) and psoriasis area severity index (PASI) were assessed apart from baseline at weeks 16, 28, and 40.RESULTS: NAPSI median score significantly decreased from 73.0 (range: 12.0-151.0) at baseline to 37.0 (range: 7.0-92.0) at week 16, to 9.0 (range: 0.0-32.0) at week 28, and to 0.0 (range: 0.0-12.0) at week 40. Median PASI score decreased from 23.9 (range: 10.6-45.5) at baseline to 0.0 (range: 0.0-5.2) at week 40. NAPSI median improvement was of 42.5% (range: 21.9-64.9%) at week 16, 86.3% (range: 75.0-100.0%) at week 28, and 100.0% (range: 91.0-100.0%) at week 40. PASI score showed a significant median improvement of 76.9% (range: 10.3-90.3%) and 100.0% (range: 71.7-100.0%), at weeks 16 and 40, respectively.CONCLUSION: Although this study may be considered as preliminary, data suggest that ustekinumab is very effective in nail psoriasis.