Clinical Differentiation of Traumatic Onycholysis from Inflammatory Nail Disease: A Comprehensive Review of Diagnostic Indicators, Chronicity, and Treatment Implications

Background: Onycholysis is a common clinical sign rather than a diagnosis. Distinguishing nail plate separation caused by mechanical trauma from onycholysis associated with inflammatory nail disease, principally psoriasis, lichen planus and eczematous or contact dermatitis, determines investigation and treatment, yet the features used for this purpose are rarely appraised critically. Objective: To synthesise the evidence on clinical, historical, anatomical, onychoscopic and temporal indicators that may differentiate traumatic from inflammatory onycholysis, and to examine how chronicity and etiology influence treatment and long-term outcomes. Evidence synthesis: Comprehensive narrative review. PubMed was searched through 27–28 October 2026, supplemented by Crossref metadata verification, publisher and repository pages and manual citation chasing. Embase, Scopus, Web of Science and the Cochrane Library were not accessible. Features were classified as validated discriminators, supportive, nonspecific, markers of secondary complication or theoretical. A total of 111 sources were cited. Key findings: Only two original studies identified compared traumatic with psoriatic onycholysis directly (60 patients and 60 fingernails, respectively), and neither reported sensitivity or specificity. The best-supported discrimination was between onychomycosis and non-fungal onycholysis: border spikes and longitudinal striae, with reported sensitivity of 57.5–75.7% and specificity of 88.2–94.1% in one toenail study. A smooth, non-erythematous border and absent matrix signs favour trauma; an erythematous rim, oil-drop discolouration, pitting, dilated hyponychial capillaries and extra-ungual disease favour psoriasis; and abundant, adherent nail bed scale after clipping was associated with psoriasis in one retrospective study. Nail lichen planus is usually accompanied by matrix signs, and acrylate or hardener contact dermatitis can mimic psoriasis. Onychomycosis is more prevalent in psoriasis (odds ratio 1.68), and microbial colonisation frequently complicates separation. No validated chronicity threshold exists; keratinisation of the exposed bed ('disappearing nail bed') may impair reattachment but is neither universal nor necessarily irreversible. Treatment evidence for mechanical onycholysis is limited to uncontrolled series, while psoriasis trials report composite nail scores rather than onycholysis-specific outcomes. Conclusion: No single feature reliably differentiates traumatic from inflammatory onycholysis. Diagnosis should integrate history, 20-nail and extra-ungual examination, onychoscopy and mycology, with reassessment when new attached plate fails to grow. Prospective diagnostic accuracy studies with explicit reference standards are needed.