Onychomadesis: A Rare Manifestation of Coxsackievirus A6 Infection in an Adult Patient.

Hand, foot, and mouth disease (HFMD) is a self-limiting viral illness predominantly affecting children under 10 years of age, with peak incidence in those aged one to four years. Recent outbreaks of Coxsackievirus A6 (CVA6) have increased its incidence across all age groups, including adults. Onychomadesis, a proximal nail plate detachment due to transient matrix arrest, is a recognized but underreported delayed complication of HFMD. We report a case of a 60-year-old man who developed onychomadesis three weeks after clinical recovery from CVA6-induced HFMD. Initial symptoms included fever, sore throat, gastrointestinal disturbances, and vesiculopapular lesions on the hands, feet, scalp, and oropharynx. He later presented with Beau's lines, onycholysis, and complete nail shedding involving all 10 fingernails and two toenails on each foot. Conservative management led to complete nail regrowth within eight to 12 weeks. Although the pathophysiology of HFMD-associated onychomadesis is not fully understood, potential mechanisms include direct viral cytotoxicity, localized inflammation, and systemic stress. CVA6 has been increasingly linked to adult cases, often with more severe mucocutaneous and nail manifestations compared to other serotypes. This case highlights CVA6 as an important and emerging cause of onychomadesis in adults following HFMD. Clinician awareness is essential for timely recognition, appropriate patient reassurance, and avoidance of unnecessary investigations. Further studies are needed to explain the underlying mechanisms and risk factors.