Often made clinically; a bacterial culture may be useful to determine organism and its sensitivity to antibiotics.
Differential Diagnosis
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The term paronychia refers to inflammation of the nail fold surrounding the nail plate and can be acute or chronic.
Onychomycosis refers to an infection of the fingernails or toenails caused by various fungi, yeasts, and molds. In contrast, the term tinea unguium refers specifically to nail infections caused by dermatophytes.
Often made clinically; a bacterial culture may be useful to determine organism and its sensitivity to antibiotics.
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Pathogenesis
Acute paronychia usually results from an infection caused by Staphylococcus aureus; less commonly by streptococci or Pseudomonas species.
The condition may occur spontaneously, or it may follow trauma or manipulation, such as nail biting, a manicure, or removal of a hangnail.
Clinical Manifestations
Acute paronychia is heralded by the rapid onset of bright red swelling of the proximal or lateral nail fold behind the cuticle with no evidence of chronic nail dystrophy.
A throbbing, tender, and intensely painful lesion often results (Fig. 22.9).
Chronic paronychia results from a combination of chronic moisture, irritation, and trauma to the cuticle and proximal nail fold.
It occurs much more often in women than in men, and it is particularly common in persons whose hands are frequently exposed to a wet environment, such as housewives, domestic workers, bartenders, janitors, bakers, dishwashers, dentists, dental hygienists, and children who habitually suck their thumbs. It is also seen more often in patients with diabetes and in persons who manicure their cuticles.
Pathogenesis
The predisposing factor is usually trauma or maceration that produces a break in the barrier (cuticle) between the nail fold and nail plate. This allows moisture to accumulate and microbial colonization and inflammation of the nail matrix ensues. The result is nail plate dystrophy.
Although Candida is frequently isolated from the proximal nail fold of patients with chronic paronychia, a primary pathogenesis for this organism has never been proven.
In fact, evidence indicates that frequently this condition is not a fungal infection at all but is actually an eczematous process. For this reason, topical steroids are often a more effective therapy than topical or even systemic antifungal agents.
Candida may play a primary pathogenic role in patients who are diabetic and those with primary mucocutaneous candidiasis.
Clinical Manifestations
Chronic paronychia usually develops slowly and asymptomatically.
Secondary nail plate changes typically occur distal to the absent or involved area of the cuticle (Fig. 22.10). Onycholysis (see earlier discussion) and a greenish or brown discoloration along the lateral borders and transverse ridging of the nails may appear.
Diagnosis
The diagnosis can generally be established based on the typical clinical appearance of the fingers and nails, as well as from the patient's history.
Various pathogens and contaminants—including Candida species, gram-positive or gram-negative organisms, or mixed bacterial flora—may be cultured from the pus obtained from under the proximal nail fold.
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Management 
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