Etiology
Bacterial causes include Staphylococcus aureus, Streptococcus, and Pseudomonas, as well as other gram-negative rods.
Viral causes include herpes simplex virus and others.
Caused by barrier disruption of the normal protective nail tissues (cuticle, nail folds).
Pathophysiology
Acute paronychia:
Barrier breakdown allows a microscopic or macroscopic portal of entry for bacteria or other microbes in the environment, into what is normally an impermeable sealed anatomic apparatus.[3]
The result is an acute (usually bacterial) infection of the soft tissues surrounding, and occasionally under, the nail plate.[1]
Chronic paronychia:
Barrier disruption in the form of lost cuticle and altered proximal nail fold facilitates exposure of water and irritant (and occasional allergic) contactants to a normally protected site under the proximal nail fold. In this warm, wet, and dark space, yeast colonize (but do not infect), and continued irritant exposure results in chronic dermatitis.
Given the proximity to the underlying matrix, secondary plate abnormalities are common.[1]
Classification
Paronychia[1]
Acute paronychia: acute, purulent infection of the nail folds and periungual tissues, usually caused by Staphylococcus aureus, although Streptococcus and certain gram-negative organisms, as well as herpes simplex virus, are occasional causes.
Chronic paronychia: chronic inflammation of the nail folds (proximal and lateral) with loss of the cuticle, eczematous dermatitis of the nail folds, secondary nail plate dystrophy, and a predisposition to secondary bacterial infections.
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