From Nail Biting to Osteomyelitis: A Pediatric Case of Distal Phalanx Infection Secondary to Onychophagia.

Onychophagia, commonly referred to as nail biting, is a body-focused repetitive behavior that occurs most frequently in children and adolescents. Although often perceived as a harmless habit, repetitive trauma to the periungual tissues can compromise the integrity of the cutaneous barrier and increase susceptibility to secondary bacterial infection. Extension of infection into deep soft tissues with associated bone involvement is uncommon, particularly within the pediatric population. We present the case of a 10-year-old female patient who arrived at the emergency department with progressive infection of the left third digit in the setting of chronic nail biting. The condition initially began as a hangnail that developed into paronychia and subsequently progressed to a felon despite outpatient treatment that included oral and topical antimicrobial therapy and incision and drainage. At the time of emergency evaluation, a substantial distal soft tissue defect with persistent drainage was observed. Plain radiographs demonstrated soft tissue disruption without clear evidence of early bony destruction. Subsequent magnetic resonance imaging identified a small distal fluid collection consistent with abscess formation and signal abnormalities of the distal phalanx suggestive of osteomyelitis. Given concern for deep infection, a hand surgery consultation was obtained, and the patient was transferred to a tertiary pediatric center. She was ultimately treated non-operatively with culture-directed antimicrobial therapy and close multidisciplinary follow-up, resulting in marked clinical improvement. This case demonstrates a rare but significant complication of chronic nail biting in a pediatric patient and reinforces the need for careful assessment of worsening digital infections. Clinicians should consider advanced imaging and early specialty involvement when periungual infections do not respond to initial outpatient management, as prompt recognition and intervention are essential to minimize long-term morbidity and preserve function.