Page 185 - Concise Pathology for Exam Preparation ( PDFDrive )

170 SECTION I General Pathology

Histopathology
1. Mumps parotitis
• Involvement is bilateral in 70% cases; affected glands are enlarged, congested and
inflamed.
• Interstitium is oedematous and shows infiltration by histiocytes and lymphocytes,
which may damage the acini. Ductal lumina may show necrotic debris.
2. Mumps orchitis
• Haemorrhage and infarction may be followed by scarring leading to sterility.
• Microscopy shows mononuclear cell infiltration.
3. Mumps pancreatitis
• Lesions may be destructive and result in parenchymal and fat necrosis.
• Neutrophil-rich inflammation is invariably present.
4. CNS
Demyelination and perivascular cuffing may be seen.

Infectious Mononucleosis
Pathogenesis
• Also known as ‘kissing disease’ or ‘Pfeiffer disease’ or ‘glandular fever’, it is a benign,
self-limiting, lymphoproliferative disease caused by Epstein–Barr virus (EBV).
• EBV infects B lymphocytes to induce reactive lymphocytosis with presence of atypical
lymphocytes known as Downey bodies.
• It is typically transmitted from asymptomatic individuals through close contact and
oropharyngeal secretions (earning it the name ‘the kissing disease’) or by sharing uten-
sils. It may also be transmitted through blood.
• The virus binds to CD21 on the surface of B cells in oropharynx.
• Circulating B cells then spread the infection throughout reticuloendothelial system, ie,
liver, spleen and peripheral lymph nodes.
• EBV infection of B lymphocytes results in a humoral and cellular response to the virus.
(The humoral immune response directed against EBV structural proteins is the basis for
the test used to diagnose infectious mononucleosis.) The T lymphocyte response is
essential for the control of EBV infection; natural killer (NK) cells and CD81 cytotoxic
T cells control proliferating B lymphocytes infected with EBV.
Clinical Features
Most commonly affects adolescents and young adults, and is characterized by lymphade-
nopathy, fever, sore throat, muscle soreness and fatigue. Other manifestations include
• Massive splenomegaly with hepatomegaly
• Petechial haemorrhages and skin rash
• Headache and loss of appetite
• Dizziness or disorientation
Complications
• Hepatitis
• Meningitis and encephalitis
• Pneumonitis
• Rupture of spleen
• EBV is also implicated in the genesis of malignancies like nasopharyngeal carcinoma,
Burkitt lymphoma and B cell variety of non-Hodgkin lymphoma.
Diagnosis
• Peripheral blood
• Absolute lymphocytosis
• Numerous large atypical lymphocytes with abundant basophilic cytoplasm showing
vacuolation with an oval, indented, folded nucleus.
• Lymph nodes
• Atypical lymphocytes in paracortical region
• Enlarged lymphoid follicles with infiltration by atypical lymphocytes

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