A paronychia is a superficial infection of the soft-tissue epithelium bordering the base of the nail fold. It is one of the most frequently encountered hand infections in all age groups and is sometimes, though less commonly, located on the toes. When a paronychia evolves to a closed pocket of pus (abscess), proper treatment involves adequate drainage. Several techniques are commonly recommended for treating the varying stages of this process. Recent overviews of paronychia have appeared (1,2,3,4,5,6), although no controlled studies comparing various treatment approaches are found. Successful management of common acute paronychia in children of any age relies on accurate and early diagnosis. Commencement of treatment is well within the repertoire of emergency physicians and pediatricians and is typically performed in the ambulatory setting.

The structure of the nail complex is illustrated in Figure 115.1A. When the seal between the proximal nail fold and the nail plate is disrupted, invading bacteria gain entry and infection ensues (Fig. 115.1B). The bacterial etiology of both pediatric and adult paronychias has been studied and reflects both skin (staphylococcal and streptococcal species) and typical oral flora. Most infections are mixed, and more than 70% include oral anaerobes (7,8). In infants, typical insults include the grasp reflex, which can cause recurrent finger paronychias and ingrown nails; tight-fitting sleeper outfits, which can cause toe paronychias; and overzealous nail trimming, which can lead to the involvement of both fingers and toes (9). Digital sucking and nail biting account for most paronychias in toddlers, preschool, and school-age children. Nail biting, hangnails, minor trauma related to work, antiretroviral therapy and artificial nails have been implicated in acute paronychias in adolescents and adults (10,11,12).

A paronychia develops over a few hours and begins laterally when a nail fold becomes painful, red, and swollen. As infection evolves, pus may accumulate under the eponychium (cuticle) and under the nail fold along the sides of the nail plate (Fig. 115.2). With further extension, pus may dissect under the nail plate, potentially compromising the ventral floor of the germinal matrix, which is primarily responsible for nail growth. Ultimately, the infection may spread to contiguous structures, causing a felon, osteomyelitis, septic tenosynovitis, or pyarthrosis (4). Adequate drainage of enclosed purulence will relieve pain, hasten resolution, and usually obviate such complications.

A paronychia may begin as cellulitis with redness, swelling, and tenderness along the edge of the nail but without frank pus accumulation. At this stage, treatment may be nonsurgical, including warm soaks, elevation, splinting, and appropriate antibiotics. Any appearance of frank pus or fluctuance warrants a drainage procedure, and little is lost by erring on the side of early drainage in uncertain cases. For small pockets of pus at the base of the nail (the most common pediatric situation), simple lifting of the eponychium off the base of the nail is sufficient. When pus accumulates below the base or side of the nail plate, additional drainage is afforded by the removal of proximal and lateral strips of nail, respectively. It is not necessary or desirable to incise periungual skin as part of the initial approach to acute paronychias. By contrast, failure of a paronychia to resolve appropriately after treatment or chronic-recurrent paronychia usually necessitates referral to a hand specialist for consideration of more
aggressive surgery (e.g., eponychial marsupialization and nail plate removal) (13).