Onychoscopy

Excerpt

Many dermatological conditions are associated with or present with nail abnormalities. Clinical examination of the nails may be insufficient to provide a straightforward diagnosis, often requiring additional evaluation for a precise diagnosis. Although biopsy-based histopathological evaluation remains the gold standard for a myriad of cutaneous diagnoses, biopsies of the nail unit can be challenging for providers and uncomfortable for patients. Dermoscopy of the nails (i.e., onychoscopy) as routine evaluation has aided the diagnosis of many lesions and limited the need for further procedural intervention. However, when further investigations (such as nail unit biopsy) become necessary, onychoscopy can also aid in intraoperative biopsy site selection.

Onychoscopy can be used to evaluate the nail matrix and nail bed, structures customarily obscured by the nail plate. The initial use of onychoscopy was often for evaluating nail pigmented lesions (i.e., melanonychia), yet the scope has expanded to include nonpigmented lesions and tumors. More literature has emphasized its use in inflammatory and infectious disorders with nail involvement, such as lichen striatus, psoriasis, connective tissue disorders, and onychomycosis. As onychoscopy can highlight changes in the nail unit that the naked eye would otherwise miss, it can optimize investigations in dermatologic diagnosis. Thus, onychoscopy serves as a diagnostic bridge between clinical morphology and histopathological evaluation of nail disorders.

Onychoscopy can be performed as non-polarized dermoscopy, polarized non-contact (dry) dermoscopy, or polarized contact (wet) dermoscopy. Non-polarized dermoscopy is used first to detect surface abnormalities, like longitudinal ridges, trachyonychia (i.e., rough and ridged nails), or surface pits. Polarized non-contact dermoscopy is used for deeper structures beneath the nail plate, allowing for a better appreciation of colors, hues, specific signs, and vessels. Polarized contact dermoscopy usually employs a linkage fluid between the dermoscopic lens and nail structure and is sometimes used for clarity and detail enhancement.