Onychoscopy in Nail Psoriasis: A Narrative Review of Diagnostic Utility, Disease Severity Assessment, Musculoskeletal Associations, and Treatment Monitoring.

Nail psoriasis is a common and clinically significant manifestation of psoriasis that may be difficult to recognize, quantify, and differentiate from other nail disorders. Onychoscopy has emerged as a non-invasive imaging technique that enables detailed visualization of nail matrix, nail-bed, and vascular abnormalities. This narrative review critically synthesized the current evidence on the diagnostic and clinical applications of onychoscopy in nail psoriasis. Literature search of PubMed/MEDLINE, Scopus, and Google Scholar was conducted, and the available evidence indicates that pitting, onycholysis, subungual hyperkeratosis, splinter hemorrhages, leukonychia, and salmon patches are among the most consistently reported onychoscopic findings. Onychoscopy enhances the detection of subtle abnormalities compared with routine clinical examination and may complement severity assessment and differential diagnosis. Associations between selected nail abnormalities, psoriatic arthritis, and enthesitis suggest a potential role in identifying patients requiring closer musculoskeletal assessment, although predictive evidence remains insufficient. Evidence supporting serial onychoscopy for therapeutic monitoring is similarly limited. Considerable methodological heterogeneity, inconsistent terminology, and predominantly small cross-sectional studies restrict definitive conclusions. Standardized examination protocols, validated onychoscopic severity indices, and prospective multicenter studies are needed to establish the diagnostic, prognostic, and monitoring roles of onychoscopy in nail psoriasis.