A teenage girl presents with mild itching and redness in her finger nail folds (Figure 164-1). The pediatrician diagnosed her with chronic paronychia, probably due to chronically pushing back her cuticles for cosmetic reasons. Behavior modification resulted in resolution of symptoms.

Paronychia is a localized, superficial infection or abscess of the nail folds. Paronychia can be acute or chronic. Acute paronychia usually presents as an acutely painful abscess in the nail fold. It is most commonly treated with incision and drainage (Figure 164-2). Chronic paronychia is defined as bring present for longer then 6 weeks duration. It is a generalized red, tender, swelling of the proximal or lateral nail folds. It is usually nonsuppurative and is more difficult to treat.

Paronychia is the most common infection of the hand representing 35 percent of all hand infections in the US.¹

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  Paronychial infections develop when a disruption occurs between the seal of the nail fold and the nail plate or the skin of a nail fold is disrupted and allows a portal of entry for invading organisms.²

  
  
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  Acute paronychia is most commonly caused by S. aureus, followed by Streptococcus pyogenes Pseudomonas pyocyanea, and Proteus vulgaris.³

  
  
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  Chronic paronychia is thought to be a multifactorial inflammatory and/or allergic phenomenon in which a variety of microorganisms, including bacteria and fungi, may be secondarily present.⁴

  
  
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  Untreated persistent chronic paronychia may cause horizontal ridging, undulations and other changes to the nail plate (Figures 164-3 and 164-4).

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  Acute paronychia commonly results from nail biting (Figure 164-5), finger sucking, aggressive manicuring (Figure 164-6), hang nails (Figure 164-7), trauma, and artificial nails.²

  
  
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  Children are prone to acute paronychia through direct infection of fingers with mouth flora from finger sucking and nail biting.

  
  
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  Patients with diabetes mellitus, compromised immune systems, or a history of oral steroid use are at increased risk for paronychia, as well as children with chronic pulmonary disease. ⁵

  
  
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  Paronychia may in some cases be a manifestation of zinc deficiency.⁶

  
  
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  Retroviral therapy use, especially indinavir and lamivudine, may be associated with an increased incidence of paronychia.⁷ Several cancer chemotherapeutic drugs, especially taxanes/anthracyclines and epidermal growth factor receptor (EGFR) inhibitors, have also been implicated.^8,9