DESCRIPTION

• Superficial inflammation of the lateral and posterior nail folds surrounding the fingernail or toenail. Develops after breakdown of barrier between nail plate and the adjacent nail fold
• Acute: characterized by pain, erythema, and swelling (1) lasting <6 weeks; usually a bacterial infection appearing after nail biting, trauma, manicures, ingrown nails, and hangnail manipulation. It also occurs as an adverse effect from several drugs. It can progress to abscess formation.
• Chronic: characterized by swelling, tenderness, cuticle elevation, and nail dystrophy and separation lasting at least 6 weeks, or recurrent episodes of acute eponychial inflammation and drainage
• Chemotherapy-associated paronychia (CAP) starts 4 to 8 weeks after chemotherapy initiation (2).
• May be considered work-related among bartenders, restaurant servers, dishwashers, nurses, and others who often wash their hands
• Usually involves one finger but drug-induced paronychia may involve multiple fingers
• Relevant anatomy: nail bed, nail plate, and perionychium
• Synonym(s): eponychia, perionychia, retronychia

Pediatric Considerations
Less common in pediatric age groups; commonly caused by trauma to periungual skin, such as thumb/finger-sucking or other injuries (Staphylococcus aureus and group A Streptococcus may be present). Paronychia is also a frequent adverse effect of BRAF and MEK inhibitor anticancer drugs.

EPIDEMIOLOGY

ETIOLOGY AND PATHOPHYSIOLOGY

• Acute: mixed aerobic and anaerobic bacterial flora in 50% of cases. Staphylococcus aureus most common and Streptococcus pyogenes; less frequently, Pseudomonas aeruginosa and other gram-negative bacteria (with chronic paronychia)
• Chronic: eczematous reaction with secondary Candida albicans (~95%)
• Pediatric age groups: mixed anaerobic (Fusobacterium, Peptostreptococcus) and aerobic infections (Eikenella corrodens, S. aureus, streptococci) from oral flora
• A paronychial infection commonly starts in the lateral nail fold.
• Acute paronychia of the fingers is often due to trauma; acute paronychia of the toes is often due to ingrown nails (3).
• Recurrent inflammation, persistent edema, and fibrosis of nail folds cause nail folds to round up and retract, exposing nail grooves to irritants, allergens, and pathogens.
• Inflammation compromises ability of proximal nail fold to regenerate cuticle leading to decreased vascular supply. This can cause decrease efficacy of topical medications.
• Early in the course, cellulitis alone may be present.
• An abscess can form if the infection does not resolve quickly.

RISK FACTORS

• Acute: direct or indirect trauma to cuticle or nail fold, manicured/sculptured nails, nail biting, thumb sucking, manipulating a hangnail, ingrown toenail
• Chronic: frequent immersion of hands in water with excoriation of the lateral nail fold (e.g., chefs, bartenders, housekeepers, swimmers, dishwashers, nurses)
• Predisposing conditions such as diabetes mellitus (DM) and immunosuppression
• Medications such as EGFR inhibitors, systemic retinoids, chemotherapy, and antiretroviral agents

GENERAL PREVENTION

• Acute: Avoid trauma such as nail biting or manipulating a hangnail. Prevent ingrown toenails.
• Chronic: Avoid exposure to allergens and contact irritants; keep fingers/hands dry; wear rubber gloves with a cotton liner. Prevent excoriation of the skin.
• Keep nails short; avoid manicures.
• Apply moisturizer after washing hands.

COMMONLY ASSOCIATED CONDITIONS

DM, eczema or atopic dermatitis, immunosuppression

HISTORY

• Localized pain or tenderness, swelling, and erythema of posterior or lateral nail folds
  • Acute: fairly rapid onset (2 to 5 days after trauma)
  • Chronic: at least 6 weeks’ duration
• Previous trauma (i.e., bitten nails, ingrown nails, manicured nails)
• Contact with herpes infections
• Contact with allergens or irritants (frequent water immersion, latex)
• Immunosuppressive therapy

PHYSICAL EXAM

• Acute: red, warm, tender, tense posterior or lateral nail fold ± abscess
• Chronic:
  • Initially appears as swollen, tender, boggy nail fold ± abscess
  • Later appears as retraction of nail fold and absence of adjacent healthy cuticle, thickening of nail plate with prominent transverse ridges known as Beau lines and discoloration; multiple digits typically involved
• Occasional elevation of nail bed or separation of nail fold from nail plate
• Fluctuance, purulence at the nail margin, or purulent drainage
• An untreated infection of the toe may lead to the formation of granulation tissue around the nail fold (3).
• Secondary changes of nail platelike discoloration
• Suspect Pseudomonas if with green changes in nail (chloronychia).

DIFFERENTIAL DIAGNOSIS

• Felon (abscess of fingertip pulp; urgent diagnosis required)
• Cellulitis
• Eczema
• Herpetic whitlow (similar in appearance, very painful, often associated with vesicles)
• Allergic contact dermatitis (latex, acrylic)
• Psoriasis (especially acute flare)
• Proximal/lateral onychomycosis (nail folds not predominantly involved)
• Retronychia
• Pemphigus vulgaris
• Acute osteomyelitis of the distal phalanx
• Reiter disease
• Pustular psoriasis
• Dermatomyositis
• Malignancy: squamous cell carcinoma of the nail, malignant melanoma, metastatic disease

DIAGNOSTIC TESTS & INTERPRETATION

None required unless condition is severe; resistant to treatment or if recurrence or methicillin-resistant S. aureus (MRSA) is suspected, then

• Gram stain
• Culture and sensitivity
• Potassium hydroxide wet mount plus fungal culture especially in chronic paronychia
• Drugs that may alter lab results: use of over-the-counter antimicrobials or antifungals

GENERAL MEASURES

• Acute inflammation without abscess: warm water soaks or antiseptic soaks, and topical antibiotics (2). Consider oral antibiotics for more severe cases that do not respond to topical treatment alone.
• Abscesses should be drained.
• Antibiotics may not be necessary for successful I&D of uncomplicated infections.
• Chronic: Keep fingers dry; apply moisturizing lotion after hand washing; avoid exposure to irritants; improved diabetic control
• Pediatric cases should be treated with systemic antibiotics.

MEDICATION

ISSUES FOR REFERRAL

• Acute: Severe infection may spread to underlying tendons, requiring evaluation and treatment by a hand surgeon as it often involves débridement, washout, or amputation, based on the severity of the infection.
• Chronic: In treatment failure, consider biopsy and/or, in cases of chronic paronychia, referral for possible partial excision of the nail fold or eponychial marsupialization with or without complete nail removal or Swiss roll technique.
• Failure to respond to therapy or chronic redness, tenderness and swelling of nail folds without abscess can be concerning for malignancy. Consider biopsy (3).

ADDITIONAL THERAPIES

Topical betaxolol 0.25% eye drops once daily on paronychia and pyogenic granuloma-like lesions covered with bandage

SURGERY/OTHER PROCEDURES

• Incision and drainage of abscess, if present. A subungual abscess or ingrown nail requires partial or complete removal of nail with phenolization of germinal matrix.
• Swiss roll technique for chronic and severe acute paronychia with runaround abscess involving both nail folds
• Recalcitrant cases may also need nail removal.

COMPLEMENTARY & ALTERNATIVE MEDICINE

Nail braces as a noninvasive alternative to nail extraction for patients with severe paronychia induced by EGFR inhibitors

FOLLOW-UP RECOMMENDATIONS

• Acute: Postdrainage care consists of warm soaks or antiseptic soaks. Follow up in 24 to 48 hours after I&D to monitor for worsening infection.
• Chronic: Avoid frequent immersion, triggers, allergens, nail biting, or finger sucking.

DIET

Maintain good glucose control.

PATIENT EDUCATION

• Avoid trimming cuticles; avoid nail trauma; and stress importance of good diabetic control and diabetic education.
• Avoid contact irritants; use rubber gloves with cotton liners to avoid exposure to excess moisture.
• Use moisturizing lotion after washing hands; do not bite nails/suck on fingers.

PROGNOSIS

• With adequate treatment and prevention, healing can be expected in 1 to 2 weeks.
• Chronic paronychia may respond slowly to treatment, taking weeks to months.
• If no response in chronic lesions, rarely benign or malignant neoplasm may be present and referral to dermatology should be considered.

COMPLICATIONS

• Acute: subungual abscess
• Chronic: nail thickening, discoloration of nail, and nail loss

SEE ALSO

Onychomycosis, Retronychia

ICD10

• L03.019 Cellulitis of unspecified finger
• L03.039 Cellulitis of unspecified toe
• L03.011 Cellulitis of right finger
• L03.012 Cellulitis of left finger
• L03.031 Cellulitis of right toe
• L03.032 Cellulitis of left toe

SNOMED

• 71906005 Paronychia (disorder)
• 444646006 Paronychia of finger
• 388983002 Paronychia of toe