Slide 15
Adverse drug reaction to tetracycline

This patient attended the sexually transmitted diseases clinic with symptoms and signs of urethritis and was prescribed a tetracycline. Seventy-two hours later the patient presented again, complaining of severe soreness on the head of the penis. A provisional diagnosis was made of genital herpes, but swabs were negative. In fact, the most likely diagnosis is a fixed drug eruption, which must be considered in any patient commencing new drug therapy immediately before a skin manifestation, even one as localised to the genitals as this. In all patients with suspected genital HSV infection, but negative virus cultures, it is essential that further diagnostic tests be performed to exclude this diagnosis. In practice, this means using type-specific serology and/or PCR testing, and in certain cases, excisional biopsy may be required to provide histological specimens to define underlying dermatological conditions.