Conditions That May Simulate Herpes Simplex Recidivans

Impetigo (Nonbullous)

Both diseases are common in the central facial region, and both begin with small clear vesicles on an inflammatory base. Herpetic lesions tend to remain fixed and discrete, and the vesicles are small, 1 to 2 mm across, tightly grouped, and persist for longer periods. Facial HSV occasionally develops secondary impetigo, causing some diagnostic confusion. A smear with a Gram stain will often show bacteria with cases of impetigo. A Tzanck smear of a blister base will show herpes virus cytopathic effect with herpes labialis. RIF test is also positive with herpes. Bacterial and viral cultures are expensive and are seldom justified.

Bacterial Paronychia and Whitlows

Differentiation of herpetic and bacterial lesions in periungual locations requires a high index of suspicion. The thick epidermis in these acral areas disguises the morphology of the herpetic lesion, which usually presents as an acute inflammatory pustule. Viral lymphangitis is common. Clear unilocular or multilocular vesicles should suggest herpes. Recurrent symptoms on the same digit in a cyclical pattern should immediately raise suspicion. Tzanck smear, RIF test, and viral cultures may be necessary.

Chancroid

Recurrent herpes genitalis can usually be distinguished from other venereal ulcers on the basis of history, inspection, and testing of a typical lesion. Early solitary lesions of chancroid (H. ducreyi) could cause confusion. Herpes lesions, unless secondarily infected, show evidence of multilocular vesicles even while regressing. Healing is usually evident at 5 to 7 days, and the lesions are almost always single. Chancroid lesions progress and become undermined. Progressive adenopathy with bubo formation is common. Adenopathy with herpes genitalis is uncommon, transient, and tends to resolve in a fashion that parallels the skin lesion. A smear from a chancroid lesion stained with Giemsa, Gram, or methyl green pyronine will reveal the bipolar organisms in half of the cases. Tzanck smear from HSV will show herpes virus cytopathic effect in a high percentage of cases and is negative in chancroid. RIF testing will increase diagnostic sensitivity. Herpes cultures are readily obtained. Cultures for chancroid are difficult and fresh material is essential. In rare cases, biopsy of an ulcer margin with special stains for H. ducreyi may be helpful. Remember, the two diseases may be simultaneously present in the same patient.

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