Acute paronychia is a painful pyogenic infection that occurs after injury or minor trauma and is characteristically caused by Staphylococcus aureus, although anaerobic organisms are also found.
Chronic paronychia presents as tender erythema of the nail folds with thickening of the tissues, loss of the cuticle, and subsequent dystrophy of the nail plate.
Repetitive micro trauma and exposure to water, irritants, and allergens, resulting in a dermatitis with subsequent colonization by yeasts, and secondary bacterial infection, are causative factors in chronic paronychia, one of the commonest nail disorders.
Another less common cause of chronic paronychia that was recently recognized is retronychia, which is characterised by disruption of the longitudinal growth of a nail due to acute injury from physical or systemic causes, with resultant embedding of the old nail in the ventral surface of the proximal nail fold as the new nail regenerates. Also, cutaneous leishmaniasis may rarely present as an unusual chronic paronychia in endemic areas.
Paronychia with pseudopyogenic granuloma may occur with systemic retinoids, antiretroviral drugs such as indinavir or lamivudine, the anti-epidermal growth factor antibody cetuximab, and epidermal growth factor tyrosine kinase inhibitors, such as gefitinib.
In rare cases it is possible that tumours are present masquerading as chronic paronychia include Bowen’s disease, keratoacanthomas, squamous cell carcinoma, enchondroma, and amelanotic melanoma.

Effective treatment

Acute paronychia requires urgent effective treatment to prevent damage to the nail matrix. If the infection is superficial and pointing, then incision and drainage without anaesthesia is possible.
Infection is often due to S. aureus, but β-hemolytic streptococci and anaerobic organisms may also be found. A swab must be taken for bacterial culture and antibiotic sensitivity, and a broad-spectrum antibiotic covering both aerobic and anaerobic organisms given.
Warm compresses with an astringent (e.g., aluminium acetate lotion, if available) can help reduce oedema and provide a hostile environment for bacteria. For deeper infections, antibiotic treatment should be started immediately, and if there has been no marked clinical improvement after 48 hours, surgical treatment undertaken. Under local anaesthesia, the proximal third of the nail plate is removed and a gauze wick is laid under the proximal nail fold to allow drainage.
Chronic paronychia is most commonly a dermatitis often associated with wet work – in domestics, cooks, bartenders, fishmongers, etc. – and may be exacerbated by contact irritants or allergens. Immediate sensitivity to fresh foods can be a factor. In children, thumb sucking may initiate the condition.
Eczema or psoriasis may predispose to chronic paronychia, as may poor peripheral circulation. Micro trauma, including overzealous manicuring of the cuticle, is also important.
The middle and index fingers of the right hand and the middle finger of the left hand are most commonly affected, but any finger may be involved. Inflammation with bolstering of the nail fold and loss of the cuticle opens a space between the nail fold and the nail plate, which commonly becomes infected with yeast, especially Candida species, and a wide range of other microorganisms.
Acute exacerbations due to bacterial infection may occur. Successful treatment relies on protection of the affected fingers from water, irritants, allergens, and trauma, together with anti-inflammatory treatment using moderately potent or potent topical corticosteroids.
Swabs for yeast and bacteria should be taken, anticandidal preparations can be useful, and antibiotic preparations may also be needed. Treatment should be continued until the inflammation has subsided and the cuticle reformed and reattached to the nail plate (3 months or more).
Applying 80% phenol with a toothpick to the groove under the proximal nail fold may encourage reattachment. Warm compresses for 10 minutes with an astringent lotion may help acute exacerbations.
For frequent acute episodes, intralesional or systemic corticosteroids plus systemic antibiotics for a week may be useful. In cases where conservative management fails, surgery or low-dose superficial radiotherapy may be considered. For cases secondary to retronychia simple avulsion of the nail plate can be curative.
Drug-induced pseudopyogenic granulomatous paronychia responds to daily topical 2% mupirocin with clobetasol propionate ointment.
Chronic paronychia due to cetuximab may respond to oral doxycycline 100mg BD.