Page 285 - Concise Pathology for Exam Preparation ( PDFDrive )

270 SECTION II Diseases of Organ Systems

(c) Pulmonary stenosis and atresia
• Pulmonary atresia: No communication between right ventricle and lungs. Blood
bypasses the right ventricle through interatrial defect.
• Pulmonary stenosis: Commonest form of obstructive CHD; comprising about
7% of all CHDs; may be an isolated defect or part of TOF.

Q. Write in detail on the aetiopathogenesis, clinical features and
laboratory diagnosis of acute rheumatic fever and rheumatic heart
disease.
Ans. Acute rheumatic fever is an acute immune-mediated multisystem disease, which
primarily involves the heart, joints, central nervous system, skin and subcutaneous
tissues.
• Its peak incidence is between 5 and 15 years and it is rare in infants and children below
the age of 5 years.
• It is more common in poor economic conditions and overcrowding.
• It progresses over course of time to chronic rheumatic heart disease.

Aetiology

• It is a delayed inflammatory response to pharyngeal infection with group A streptococci.
• The latent period between the pharyngeal infection and the onset of rheumatic fever
ranges from 1 to 5 weeks.
• Type 5 strain commonly causes rheumatic fever. The other rheumatogenic serotypes
include 1, 3, 6, 14, 18, 19 and 24.
• Antibodies develop against streptococcal antigens but cross react with cardiac myosin
and sarcolemmal membrane protein.

Pathology
Acute rheumatic fever is characterized by exudative inflammatory lesions of connective
tissue mainly involving the heart, joints and subcutaneous tissues. These exudative lesions
are replaced by scar tissue in the later or healed phase of the disease (chronic rheumatic
heart disease). All three layers (endocardium, myocardium and pericardium) of the heart
are involved resulting in pancarditis. The following pathological changes are seen in the
different layers:
• Myocardium: Myocardium shows the pathognomonic myocardial Aschoff body (focus
of swollen eosinophilic collagen surrounded by lymphocytes, plasma cells, fibroblasts,
Aschoff giant cells and large basophilic cells called Anitschkow cells, which have abun-
dant cytoplasm, round to oval nuclei with central slender wavy ribbon like chromatin;
therefore, Anitschkow cells are also called caterpillar cells). Aschoff bodies are classically
located in the interstitial connective tissue of myocardium especially in perivascular
location and may persist for many years in chronic rheumatic inflammation, especially
in those who develop severe mitral stenosis.
• Endocardium: Rheumatic endocarditis produces verrucous lesions, which heal with
fibrous thickening and adhesions of valve commissures, leaflets and chordae tendinae,
resulting in varying degrees of stenosis and regurgitation. Regurgitant streams produce
irregular thickening of the left atrium called MacCallum plaques. Mitral valve is the
most commonly involved, followed by aortic valve, and rarely, tricuspid valve. Pulmo-
nary valve is almost never involved.
• Pericardium: Serofibrinous pericarditis produces a classical ‘bread and butter’ appearance.

Clinical Manifestations

1. Sore throat: History of antecedent upper respiratory tract infection in the past
1–5 weeks.

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