Herpes simplex

Distal digital herpes simplex infection may affect the terminal phalanx as a primary herpetic 'whitlow' or start as an acute, intensely painful paronychia (Figures 5.37, 5.38). It is relatively common in dental staff, anaesthetists and those involved with the care of the mouth and upper respiratory tract in unconscious patients. Recurrent forms are generally less severe and have a milder clinical course than the initial infection.

After an incubation period of 3-7 days, during which local tenderness, erythema and swelling may develop, a crop of vesicles appears at the site of origin in the skin. The vesicles are typically distributed in the paronychia and on the volar digital skin, resembling pyogenic infection of the finger tip. Close inspection, however, will reveal the characteristic pale, raised vesicles surrounded by an erythematous border. An acutely painful whitlow may develop and extend under the distal free edge of the nail and into the nail bed. A distinct predilection for the thumb, index and ring fingers on the dominant hand has been noted, but any finger may be involved. Multiple lesions are rare. For 1014 days the vesicles gradually increase in size, often coalescing into large, honeycombed bullae. New crops of lesions may appear during this time. Vesicular fluid is clear early in the disease but may become turbid, seropurulent or even haemorrhagic within days of onset. At times, a pale yellow colour of the vesicles will suggest pyogenic infection, yet frank pus is not usually obtained. Patients complain of tenderness and severe throbbing in the affected digit. Coexisting primary herpetic infections of the mouth and finger nails suggest auto-inoculation of the virus into the nail tissues as a result of nail biting or finger sucking.

Radiating pain along the C7 spinal nerve distribution is sometimes noted before each recurrence. Lymphangitis may start from the wrist and extend to the axilla with painful lymphadenopathy. Numbness and hypo-aesthesia following the acute episode have been observed.

The diagnosis of herpetic infection can be made by examining the base of the vesicles for the characteristic multinucleated 'balloon' giant cells, in stained smears. The presence of intranuclear inclusions is also significant. Viral cultivation, usually positive within 24 hours of onset, is confirmatory; the active viral phase lasts up to 4-5 days in primary attacks but only 2-3 days in recurrent episodes.

Differential diagnosis

It is important to exclude primary or recurrent herpes simplex infection in the differential diagnosis of every vesiculopustular finger infection. The typical appearance of the lesions with disproportionately severe pain, the absence of pus in the confluent, multiloculated, vesiculopustular lesions and the lack of increased tension in the finger pulp aid in differentiating this slow-healing infection from a bacterial foreign body or paronychia.

Figure 5.37

Primary herpes simplex—herpetic 'whitlow'.

Figure 5.37

Primary herpes simplex—herpetic 'whitlow'.

Herpes The Finger

Figure 5.38

Subungual recurrent herpes simplex.

Herpes zoster infections, which may affect the proximal nail fold like herpes simplex, also involve the entire sensory dermatome. The pustules of primary cutaneous Neisseria gonorrhoeae infection may resemble herpes simplex on the rare occasion when it occurs on the finger. The diagnosis is established by positive Gram staining and bacteriological culture.

Treatment

Treatment is aimed primarily at symptomatic relief and the avoidance of secondary infection. Topical acyclovir may shorten the course of any one attack; given orally the drug may prevent recurrences while it is being taken. On cessation of the treatment relapses are unfortunately common. This is a preventable infection. Gloves should always be worn on both hands for procedures such as intubation, removal of dentures or providing oral care, despite the additional costs involved.

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