Page 186 - Concise Pathology for Exam Preparation ( PDFDrive )

7 Infections 171

• Liver
• Atypical lymphocytes in portal areas and sinusoids
• Scattered isolated/individual cell necrosis or foci of parenchymal necrosis common
• CNS
• Congestion, oedema, perivascular mononuclear cells and leptomeningeal infiltrate
• Mononucleosis test
• Includes the Monospot test and EBV antibody test (Monospot test is a heterophile
antibody test for rapid diagnosis of
• EBV; the test may be falsely negative early in the course of the infection)
Poliomyelitis
Pathogenesis
• Polio is an acute infection of both the meninges and motor neurons of spinal cord and
brainstem. Involvement of the latter may produce permanent paralysis.
• It is caused by poliovirus, which is a spherical, unencapsulated RNA virus of the entero-
virus genus. There are three major strains of poliovirus: types I, II and III.
• Poliovirus, like other enteroviruses, is transmitted by the faecal-oral route. It first infects
tissues in the oropharynx where it infects cells by binding to CD155, is secreted into
saliva and swallowed, and then multiplies in intestinal mucosa and lymph nodes, caus-
ing a transient viraemia and fever.
• Virus spread to the nervous system may be secondary to viraemia or by retrograde trans-
port of the virus along axons of motor neurons. Circulating viruses cross the blood–brain
barrier and cause inflammation (itis) of the grey matter (polio) of the spinal cord (my-
elin). Motor neurons are involved. In fatal cases, destruction is found in cerebral ganglia,
reticular formation, cerebellar nuclei, hypothalamus, thalamus and cerebral cortex.
Clinical Features
• Nonspecific symptoms, eg, moderate fever, headache, vomiting, constipation, coryza
and sore throat occur 6–20 days after exposure.
• The illness may subside entirely (minor or abortive poliomyelitis), abate temporarily or
progress directly to involve the CNS (major poliomyelitis) 2–6 days after onset, which
may be paralytic or nonparalytic.
• Early in paralytic poliomyelitis the patient exhibits
• Signs of meningeal irritation
• Weakness
• Hyperesthesia (increased sensitivity to stimuli)
• Severe muscle pain
• Spasm of involved muscles or accentuated tendon reflexes
Pathology
Gross: Swelling, softening, congestion and petechial haemorrhages in the organ affected
Microscopy: Congestion, interstitial oedema and infiltration by lymphocytes

German Measles (Rubella)
Pathogenesis
• Also called ‘3-day measles’, it is transmitted by close personal contact and usually pres-
ents with fever, headache, arthralgias and painful post-auricular lymphadenopathy.
• This is followed by the onset of a maculopapular rash, which begins on head and
spreads downwards.
• In pregnant women, it can cause
• Cardiac anomalies, such as, ventricular septal defect and patent ductus arteriosus
• Cataract
• Deafness
• Mental retardation and delayed milestones
• Seizures
• Microcephaly
• Intrauterine death

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