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SUMMARY
Viral nail infections are caused by direct viral invasion of the nail unit, by hematogenous spreading of the virus to the nail unit, or due to a systemic reaction on virus infection.
Human papilloma and herpes simplex viruses may spread to other locations and other people by direct or indirect contact.
Complete recovery is the rule, even if left untreated.
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TIPS FOR TREATMENT
The benign course mostly justifies conservative management awaiting spontaneous resolution.
In herpetic whitlow, coverage with dry dressing is advisable to prevent spreading.
Topical antiviral treatments do not provide a relevant benefit in herpetic whitlow.
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PITFALLS AND CAUTIONS
Aggressive treatments of warts are not recommended to prevent nail dystrophy.
Disinfect the dermoscope thoroughly after use.
Don’t incise vesicles in herpetic paronychia to avoid spreading the virus and to prevent bacterial superinfection.
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Several mechanisms play a role in virus-induced nail abnormalities. The most common mechanism is direct viral invasion of the nail unit, such as in warts or herpetic whitlow. Viral presence in the nail may also be the consequence of viremia resulting in local ungual viral replication. Hand–foot–mouth disease (HFMD) is an example of this. Finally, viral infections may lead to nail involvement without presence of the virus in the nail unit itself. Many viral systemic diseases may induce unspecific secondary nail changes but also more virus-specific nail changes occur. Toga virus is a well-described example of a virus responsible for inducing rather specific nail changes.
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Direct viral infections of the nail unit may result in acute or chronic infections. Viral causes of paronychia, such as herpes simplex virus (HSV), should be considered when acute paronychia is unresponsive to antibiotics.1 Human papilloma virus (HPV) induces common warts, a typical chronic infection with a clinical picture mostly devoid of a noticeable immune reaction. In viremia-induced infections, like HFMD, nail changes occur within the context of other symptoms of the skin or other organs. Here, nail changes often involve several, but not all, nails and may become visible weeks later. Nail abnormalities induced by systemic viral infections may lead to non-specific signs in all nails, like Beau’s lines or onychomadesis, occurring after several weeks. More specific nail disorders attributable to certain viral infections mostly occur earlier, such as subungual hemorrhage, ...