Page 488 - Textbook of Pathology, 6th Edition

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Figure 17.10 A, Gross appearance of bronchopneumonia contrasted
with that of lobar pneumonia. B, The pleural surface of the specimen of the
lung shows serofibrinous exudate. The sectioned surface shows multiple,
small, grey-brown, firm, patchy areas of consolidation around bronchioles
(arrow). while the intervening lung is spongy.

B. VIRAL AND MYCOPLASMAL PNEUMONIA ETIOLOGY. Interstitial pneumonitis is caused by a wide
(PRIMARY ATYPICAL PNEUMONIA) variety of agents, the most common being respiratory syncytial
virus (RSV). Others are Mycoplasma pneumoniae and many
Viral and mycoplasmal pneumonia is characterised by viruses such as influenza and parainfluenza viruses,
SECTION III
patchy inflammatory changes, largely confined to interstitial adenoviruses, rhinoviruses, coxsackieviruses and cyto-
tissue of the lungs, without any alveolar exudate. Other terms
megaloviruses (CMV). Occasionally, psittacosis (Chlamydia)
used for these respiratory tract infections are interstitial and Q fever (Coxiella) are associated with interstitial
pneumonitis, reflecting the interstitial location of the pneumonitis.
inflammation, and primary atypical pneumonia, atypicality Infections of the respiratory tract with these organisms
being the absence of alveolar exudate commonly present in are quite common. In most cases, the infection remains
other pneumonias. Interstitial pneumonitis may occur in all confined to the upper respiratory tract presenting as common
ages. Most of the cases are mild and transient; exceptionally cold. Occasionally, it may extend lower down to involve the
it may be severe and fulminant. interstitium of the lungs. The circumstances favouring such

Systemic Pathology

Figure 17.11 Microscopic appearance of bronchopneumonia. The bronchioles as well as the adjacent alveoli are filled with exudate consisting
chiefly of neutrophils. The alveolar septa are thickened due to congested capillaries and neutrophilic infiltrate.