Abstract
INTRODUCTION: Onychotillomania is a body-focused repetitive behavior disorder characterized by compulsive trauma to the nail unit. While manual manipulation is well recognized, oral-induced mechanisms remain undocumented. We describe a novel subset involving frictional trauma from the teeth, which we term onychotillomania dentata. CASE PRESENTATION: An 11-year-old female presented with a 1-year history of progressive thumbnail dystrophy. Clinical history revealed a habitual behavior occurring predominantly at night: inserting the thumbs into the mouth and rubbing the nail plates against the lower incisors in a repetitive anteroposterior motion. The patient described the behavior as soothing and unconscious. Signs of concomitant onychophagia were also present. Examination demonstrated central nail plate concavity, lamellar splitting, periungual erythema, and localized subungual hyperkeratosis. Dermoscopy revealed lamellar onychoschizia, linear furrows, and compact subungual debris. Behavioral counseling was initiated, including thumb guards during sleep and positive reinforcement strategies. Oral n-acetylcysteine (600 mg every 12 h) was prescribed as adjunctive therapy. Referral to pediatric psychodermatology was recommended for behavioral assessment and initiation of habit-reversal training. CONCLUSION: Onychotillomania dentata represents a previously undescribed pattern of nail trauma within the broader spectrum of onychotillomania. While classical onychotillomania typically results from manual manipulation, onychotillomania dentata is distinguished by repetitive oro-digital friction. Clinical features include central concavity, lamellar splitting, and linear furrows along the axis of mechanical trauma. Diagnosis often relies heavily on clinical morphology and dermoscopy, especially as many patients may deny their behavioral habit. Early recognition is crucial to avoid misdiagnosis and unnecessary treatment. Additionally, chronic mechanical friction may pose a risk of dental damage, including enamel erosion. Management involves behavioral modification strategies, pharmacologic support when appropriate, and interdisciplinary psychodermatologic care.