Two weeks ago, a 54-year-old man developed a cold sore, which resolved uneventfully. He now complains of a nonpruritic skin rash. Examination reveals raised red lesions resembling hives, some with clear fluid bullae. They are located on his hands, including the palms, and his forearms and anterior tibia. The best way to confirm your suspected diagnosis is by:
Viral culture of blister fluid.
+Smear of blister fluid for Gram stain.
+Tzanck preparation of blister fluid to look for multinucleate giant cells.
+Full thickness skin biopsy of involved area.
+Wood's light examination of involved areas.
Herpes simplex infection may precede erythema multiforme (EM). Affected patients may have recurrent bouts of the disease with each episode of herpes. The virus is not found in the blisters of EM, nor are fungi or bacteria. Immunofluorescent studies of a skin biopsy showing Ig-complement deposits at the dermoepidermal junction confirm the diagnosis. In mild cases, clinical diagnosis and outpatient treatment with topical steroids and close follow-up are sufficient. Other causes, such as drugs and malignancy, should be considered. Severe cases require hospitalization.