case14-HSV1

case14-HSV1 - Lydyard, Peter; Cole, Michael; Holton, John;...

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1. What is the causative agent, how does it enter the body and how does it spread a) within the body and b) from person to person Causative agent Herpes simplex virus type 1 is a herpesvirus. The Herpesviridae family of viruses is characterized by having a double-stranded DNA genome of 125–240 kb in size (i.e. enough genetic material to encode for 150–200 viral proteins), surrounded by an icosahedral capsid , and a lipid envelope . The space between the capsid and the envelope is referred to as the tegu- ment. This contains a number of virally encoded proteins, some of which are thought to play a role in viral transport within nerves (see later). Embedded within the envelope are several virally encoded glycoproteins, which are important for binding of the virus to target cells and subsequent cell entry. Thus far, eight herpesviruses have been identified as pathogens of humans – see Table 1 in the Epstein-Barr virus case (Case 9). The genome sequences of HSV-1 and HSV-2 share considerable homol- ogy and the biological properties of these two viruses are indeed similar. Disease arising from infection with each virus is clinically indistinguish- able. However, HSV-1 infections tend to occur ‘above the waist,’ that is Case 14 Herpes simplex virus 1 (HSV-1) A 13-year-old boy was taken to the hospital’s emergency department by ambulance. His mother had called out the emergency services as he had had a generalized fit that morning. Since he stopped fitting, he had been very drowsy. His mother reported that he was well until 24 hours previously, when he started acting strangely – including wandering around the house not knowing where he was. He vomited once the previous evening, but otherwise has not complained of any specific problems. On examination, he was drowsy but responsive. He was unable to give a coherent history, and had difficulty in understanding where he was. He was febrile (38.5 C), but had no other abnormal physical signs. An intravenous line was set up, and he was started on empirical antibiotic therapy, together with intravenous aciclovir. A magnetic resonance imaging ( MRI ) scan of his brain was organized for later in the day, which was reported by the duty radiologist as showing ‘an area of low attenuation in the right temporal lobe extending into the frontal lobe gray matter. There was mass effect with displacement of the right middle cerebral artery, appearances most compatible with herpes simplex encephalitis .’ A lumbar puncture was performed that evening. The cerebrospinal fluid (CSF) was noted to be slightly blood- stained. The microbiology technician reported the presence of 500 ¥ 10 6 red blood cells l –1 , 57 ¥ 10 6 white cells l –1 , predominantly lymphocytes, a normal CSF sugar, and a CSF protein level of 4.8 g l –1 , just above the upper limit of normal. No organisms were seen on a gram- stained film. A provisional diagnosis of herpes simplex encephalitis
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This note was uploaded on 09/14/2011 for the course PHARM mb taught by Professor Staff during the Spring '11 term at UCSD.

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case14-HSV1 - Lydyard, Peter; Cole, Michael; Holton, John;...

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