Part II. Changes in Nail Structure and Growth as Signs of Systemic Disease.

Changes in structure and growth of the nail unit may serve as clinical clues to underlying systemic disease. Pathophysiology may involve disruption to nail vascularization, metabolism and nutrition, inflammation, infections, and genetic disorders. Patients with nail changes often present with concurrent cutaneous findings, either of which or both together may indicate underlying systemic disease. Nail involvement may also correlate with systemic disease activity and severity. Dermoscopy and bedside diagnostic tools can aid in diagnosis. Prompt interdisciplinary referrals are important for systemic disease diagnosis and improved patient outcomes. In Part II of this continuing medical education series, we outline systemic diseases associated with changes in nail structure and growth, including clubbing, koilonychia, Beau's lines/onychomadesis, onycholysis, onychorrhexis, and pterygium inversum unguius. In addition, we describe their pathophysiology, clinical features, and recommendations for workup.