Fingernail psoriasis reconsidered: A case-control study

Background: Literature concerning clinical signs and frequency of nail psoriasis is incomplete. Recent studies focus only on signs included in the Nail Psoriasis Severity Index (NAPSI). Objective: We sought to describe clinical characteristics of fingernail psoriasis in comparison with healthy controls. Methods: We collected data on 49 patients with fingernail psoriasis who visited our outpatient department and 49 control subjects, through questionnaires and clinical examination. The disease severity was measured by the NAPSI. Results: Mean NAPSI score in patients and control subjects was 26.6 and 3.6, respectively. Most items included in the NAPSI were specific for nail psoriasis. Onycholysis and splinter hemorrhages were most frequently observed. Leukonychia was more frequent in control subjects. Longitudinal ridges and Beau lines are not included in the NAPSI but are significantly more frequently seen in patients than in control subjects. Limitations: Limited sample size was a limitation. Conclusion: The NAPSI was able to discriminate patients with fingernail psoriasis from healthy control subjects. Onycholysis and splinter hemorrhages were the most prevalent fingernail changes in psoriatic patients. Leukonychia was more frequently observed in control subjects, which raises the question of whether leukonychia should remain in the NAPSI. On the other hand, longitudinal ridges and Beau lines occurred more frequently in psoriasis but are not included in the NAPSI.