Page 181 - Concise Pathology for Exam Preparation ( PDFDrive )

166 SECTION I General Pathology

• Fibrosis: Organization of intra-alveolar exudate may convert affected lung into solid
fibrous tissue.
• Bacteraemic dissemination: Dissemination of bacteria may lead to endocarditis,
pericarditis, meningitis, suppurative arthritis and formation of metastatic abscesses in
various organs, eg, kidneys, spleen, etc.

Primary Atypical Pneumonia (Viral and Mycoplasma Pneumonia/
Interstitial Pneumonitis)
It is defined as an acute febrile respiratory disease which manifests with patchy inflamma-
tory changes confined to alveolar septae and pulmonary interstitium. Causative organisms
include
• Mycoplasma pneumoniae
• Influenza virus type A and B
• Respiratory syncytial viruses, adenovirus, rhino virus, rubeola and varicella virus
• Chlamydia
• Coxiella burnetii

Predisposing Conditions

Malnutrition, alcohol intake and diminished immunity

Clinical Features
• Nonspecific
• May mimic upper respiratory tract infection or present as an acute nonspecific febrile
illness manifesting with fever, headache, myalgias
• May present as a life-threatening infection in immunocompromised individuals

Gross Morphology

• Lungs are red-blue, congested and subcrepitant; pleural involvement is rare.
• Involvement may be patchy or lobar; unilateral or bilateral.

Microscopy
• Inflammation is restricted to alveolar walls and the alveolar space appears free of exudate
(therefore, also called atypical pneumonia). Alveolar walls show presence of mononu-
clear inflammation (lymphocytes, histiocytes and plasma cells).
• Alveolar spaces may sometimes demonstrate intra-alveolar proteinaceous material or a
pink hyaline membrane lining the alveolar septal walls.
• Superimposed bacterial infections lead to picture-simulating bacterial pneumonias.
• Cytomegalovirus-induced atypical pneumonia is characterized by presence of giant
cells with intranuclear/ intracytoplasmic inclusions.

Q. Write briefly about syphilis.

Ans. Though a venereal disease, syphilis involves multiple systems. It is often called ‘the
great imitator’ because many of its signs and symptoms show a major overlap with those
of other diseases.
Causative agent is Treponema pallidum (Fig. 7.6). The organism has the following characteristics:
• An axial protoplasmic flagella wound around a slender helical protoplasm.
• Confirmation of diagnosis by dark field examination, silver stains and immunofluores-
cence examination.
• Sexual transmission (through bacteria-laden secretions/intimate contact).
• Transplacental transmission (congenital syphilis).

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