Herpes simplex infection and gingivostomatitis

What it is

Herpes simplex is a common viral infection with two types split by site. HSV type 1 gives lip and skin lesions and favors the mouth and nose (upper is 1). HSV type 2 gives genital lesions and favors the genitalia, buttocks and thighs (low is 2). After the first infection the virus stays latent and can reactivate later.

How it presents

The lesion is painful, grouped vesicles on an erythematous base, going on to ulceration.

• In the mouth of a child this is herpetic gingivostomatitis.
• HSV-1 also gives herpes labialis, with cold sores and fever blisters.
• On the eye, HSV-1 gives a dendritic ulcer, that is HSV epithelial keratitis: unilateral ciliary congestion with no discharge and reduced VA, while the cornea otherwise seems to be clear. There may be a history of past primary infection such as perioral vesicles, and a recent immunosuppression or illness.

How it is diagnosed

The tests for HSV are the Tzank smear, PCR and direct fluorescent antibody. On the eye the dendrites will only be seen if staining with fluorescein. When encephalitis is the question, the CSF is lymphocyte predominant and the test is HSV PCR on CSF.