At the 2025 Dermatology Days of Paris conference, held from 2 to 6 December 2025, in Paris, France, Bertrand Richert, MD, PhD, professor in the Dermatology Department, Brugmann and Saint Pierre University Hospitals, Université Libre de Bruxelles, and Queen Fabiola Children’s University Hospital in Brussels, Belgium, reviewed recent diagnostic and therapeutic developments in nail disorders, highlighting their practical implications for routine dermatology practice.

Common Nail Diseases

Two common inflammatory skin diseases may be exclusively localised to the nail area: lichen planus and psoriasis.

Nail lichen planus may lead to chronic lesions with substantial functional impairment. When the disease is confined to the nail, intralesional triamcinolone acetonide is now considered the first-line therapy in both adults and children.

The management of nail psoriasis depends on the number of affected nails. Systemic therapy is recommended when more than three nails are involved. In such cases, cyclosporine provides the most rapid clinical response. Psoriasis biologic therapies may subsequently be considered, with no clear differences in efficacy reported among the available agents.

Another relatively rare and little-known condition is retronychia.

According to Richert, trauma, circulatory disorders, and inappropriate footwear may disrupt onychomadesis. Instead of shedding, nail growth stops, and a new nail plate forms beneath the old plate, resulting in stacking of nail plates, irritation, and exudation. Although retronychia may resolve spontaneously, it can become chronic and dystrophic, producing a characteristic shrimp or lobster appearance. Treatment with topical corticosteroids or intralesional injections often leads to resolution.

Paediatric Nail Disorders

In children, traumatic and infectious causes and ingrown nails are among the least frequent reasons for paediatric hospital consultations. The most common paediatric nail disorders, in descending order, are Beau’s lines and onychomadesis, followed by trachyonychia, longitudinal melanonychia, and congenital nail malalignment.

Beau’s lines, defined as transverse grooves of varying depth across the nail plate, and onychomadesis, defined as detachment of the nail plate from the nail matrix and nail bed, are associated with acute or severe medical events, such as fever, that slow or halt nail growth.

Trachyonychia is characterised by rough, longitudinally ridged, thin, and brittle nails.

Longitudinal melanonychia presents as pigmented bands. It may be functional but can also be associated with naevus or melanoma, warranting excision followed by histologic analysis.

Congenital nail malalignment represents one recognised aetiology of nail deviation, alongside acquired forms, often postsurgical, and hereditary pincer nails. Spontaneous resolution occurs in approximately 50% of affected children, supporting a watch-and-wait approach before considering surgery. Surgical realignment is effective at any age and severity, although it is a major procedure.

In all cases, Richert emphasised that paediatric nail disorders are most often benign and regress spontaneously or with mild conservative treatment.

Ingrown Nails

Improper trimming at the nail edges may lead to the formation of a nail spike, sometimes described as a harpoon nail, which becomes inflamed and results in an ingrown nail. When persistent, the nail may tunnel through the surrounding tissue and reemerge distally.

Currently, there is no universal treatment approach for ingrown nails. Chemical matricectomy remains the reference standard. Phenol and trichloroacetic acid provide comparable outcomes, although phenol is associated with lower morbidity. When conservative measures fail, narrowing of the nail plate or excision of the surrounding soft tissue may be considered. These techniques allow intervention without damaging the nail plate, thereby reducing the risk for nail deformity. Other surgical approaches more readily sacrifice periungual soft tissue, including U-shaped excision around the nail.

Nail Tumours

Squamous cell carcinoma is the most common malignant tumour of the nail unit. Its slow progression often leads to delayed diagnosis. Conservative surgery with complete excision now yields favourable outcomes and is preferred, with amputation reserved for cases involving bone invasion. Approximately two thirds of these tumours are associated with human papillomavirus (HPV) infection, particularly HPV 16. Infection occurs through genitodigital autoinoculation or partner-mediated transmission.

Longitudinal melanonychia should most often raise suspicion for nail melanoma. However, 20%-30% of nail melanomas are amelanotic. As Richert noted, a pink exophytic lesion of the nail apparatus should prompt a biopsy to avoid a missed diagnosis.

Other nail tumours also pose diagnostic challenges because clinical features may resemble benign conditions. Epithelial nail tumours include onychopapilloma, which is generally benign, and polydactylous onychopapilloma associated with a BAP1 mutation. The latter should prompt genetic counselling and evaluation for associated cutaneous melanoma, uveal melanoma, and mesothelioma.

Unexplained nail dystrophy that does not respond to initial treatment, pain, changes in nail plate colour, or involvement of periungual soft tissue can also be warning signs.

This story was translated from Univadis France, part of the Medscape Professional Network.