Slide 2
A single initial lesion in primary genital herpes

In some patients with primary genital herpes, the initial lesion is large and solitary rather than multiple and small ulcers as in slide 1. In this patient with primary genital herpes, the differential diagnosis is with other causes of ulcerative genital infection, namely, syphilis, chancroid, lymphogranuloma venereum, or non-infectious causes such as a fixed drug eruption (e.g. to tetracycline), Lichen planus or trauma. It is essential that a full history of possible sexual exposure, including a travel history, is taken along with a proper dermatological history and examination. Empirically, oral antiviral treatment should be instigated on the basis of probability of the diagnosis, with the emphasis on over-treatment of cases which will turn out not to be HSV, rather than under-treatment (and the increased risk of further lesional development).