What is paronychia?

What is Paronychia?

Paronychia is an inflammation of the nail folds (the tissue surrounding the nail) affecting fingers or toes, which can be acute (bacterial infection after nail barrier breach) or chronic (irritant contact dermatitis lasting ≥6 weeks). 1, 2

Clinical Definition and Pathophysiology

Paronychia specifically involves inflammation of one or more of the three nail folds—the proximal and/or lateral folds of tissue surrounding the nail plate. 2, 3

Acute Paronychia

• Acute paronychia develops when the protective seal between the nail fold and nail plate is disrupted, creating a portal of entry for invading organisms. 2, 4
• The condition is caused by polymicrobial infections, with both gram-positive organisms (Staphylococcus aureus, Streptococcus) and gram-negative bacteria implicated. 1, 2, 3
• Viral infections, particularly herpetic whitlow, can also cause acute paronychia. 3
• The thumbs and great toes are most frequently affected, likely due to repeated trauma. 1

Chronic Paronychia

• Chronic paronychia is characterized by symptoms lasting at least 6 weeks and represents an irritant contact dermatitis rather than a primarily infectious process. 1, 2
• The main pathophysiologic factor is the disappearance of the cuticle, which normally provides a protective barrier. 3, 5
• Repeated bouts of inflammation lead to fibrosis of the proximal nail fold with poor cuticle regeneration, creating a vicious cycle of further exposure to irritants. 5
• This condition commonly affects individuals with wet occupations, such as housekeepers, dishwashers, bartenders, florists, bakers, and swimmers. 1, 2
• Chronic paronychia of the fingernails occurs in patients with chronic water immersion or allergic reactions to foods, where swelling of the posterior nail fold causes cuticular detachment from the nail plate. 6

Secondary Infections and Complications

• Up to 25% of paronychia cases have secondary bacterial or mycological superinfection, which must be considered in treatment planning. 1, 7
• In chronic paronychia, bacterial or fungal colonization (particularly Candida species) represents secondary colonization of chronically irritated tissue rather than the primary cause. 6, 3, 4
• Onychomycosis due to moulds (Fusarium) or dematiaceous fungi (Scytalidium dimidiatum) are often associated with paronychia. 3

Associated Conditions

• Paronychia frequently occurs in association with ingrown toenails (onychocryptosis), where the inflammation is secondary to the nail pathology. 1, 8, 4
• The condition is a frequent side-effect of chemotherapies and targeted therapies (particularly EGFR inhibitors). 1, 3
• Paronychia can be a complication of systemic conditions and certain medications. 9

Clinical Presentation

• Acute paronychia presents with redness, tenderness, swelling, and potentially abscess formation with purulent discharge. 8, 2
• Chronic paronychia manifests as persistent inflammation with nail changes including thickening, ridging, and discoloration. 9, 5
• Infection and inflammation in the area of the nail matrix eventually lead to proximal nail dystrophy in chronic cases. 6