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Lung-nontumor

Infections

Herpes simplex pneumonia

Reviewer: Elliot Weisenberg, M.D. (see Reviewers page)
Revised: 30 December 2011, last major update September 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.

Definition
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● Herpes simplex virus (HSV), serotypes HSV-1 and HSV-2, cause acute infection followed by latent phase that may reactivate to infectious form
● See also Skin-nontumor chapter
● HSV-1 and HSV-2 are alpha group herpes viruses with similar genotypes but serologic differences; may both infect the lung
● HSV-1 usually affects oral pharynx; HSV-2 usually causes genital infection
● Virus spreads via sensory neurons where latent infection is established
● Reactivation may be symptomatic or asymptomatic, virus spreads via nerves to mucus membranes or skin, where it replicates
● Newborns (see below), patients with impaired mucosal defenses, burn patients, trauma patients, and severely immunocompromised patients are at greatest risk
● Also associated with coexisting bacterial pneumonia (J Crit Care 2011;26:432e1)
● Also be caused by intubation of patient with active oral disease
● Immunostains, PCR, culture or electron microscopy can confirm the diagnosis if necessary

Gross description
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● Diffusely firm lungs with small yellow/red necrotic areas

Gross images
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Various images

Micro description
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● Interstitial pneumonia with necrosis of bronchial and alveolar epithelium and acute and chronic inflammatory infiltrate
● Occasional intranuclear viral inclusions at edge of necrotic areas
● Neutrophilic infiltrates may resemble bacterial bronchopneumonia, but Cowdry type A or B nuclear inclusions are generally diagnostic

Micro / cytology images
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Left-H&E; right-immunostain highlights HSV+ cell in broncheoalveolar lavage

Neonatal HSV pneumonia

General
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● Infection is acquired during vaginal delivery, symptoms develop 5 days post partum
● Delivery via caesarian section is now mandatory if active genital disease suspected during delivery
● Incidence of 1 in 3,200 births
● Disseminated disease is typical, with prominent findings in liver and adrenal glands (originally described as “hepatoadrenal necrosis”)
● 40-50% develop pneumonia
● In pre-antiviral era, 85% died, reduced to 30% due to acyclovir

Gross description
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● Normal

Micro description
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● Patchy necrosis; minimal inflammatory response; not bronchocentric

End of Lung-nontumor > Infections > Herpes simplex pneumonia

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