Rheumatic Heart Disease (RHD) - Complete Exam Guide

What is it, in simple terms?

Strep throat (Group A Streptococcus) → Acute Rheumatic Fever → Permanent Valve Damage = Rheumatic Heart Disease

• Goldman-Cecil Medicine explains it simply: "Rheumatic heart disease is the long-term sequela of a single episode or repeated episodes of acute rheumatic fever."

Step 1: How Does Strep Throat Cause Heart Damage?

1. Group A Streptococcus (GAS) infects the throat (NOT the skin - skin strep infections never cause RHD)
2. The bacteria have surface proteins (M proteins) that look similar to proteins in the human heart (cardiac myosin, tropomyosin, laminin)
3. The immune system makes antibodies against the bacteria...
4. ...but those same antibodies attack heart tissue by mistake
5. CD4+ T cells infiltrate the valves and myocardium, causing inflammation

Key point: Streptococci are completely absent from the heart lesions - this is a pure immune/autoimmune injury, not direct bacterial infection.

Step 2: Acute Rheumatic Fever (ARF)

Who gets it?

• Most common in children 5-15 years old
• Equally in males and females
• Common in developing countries / overcrowded conditions

The 5 Major Manifestations (remember: JONES)

Revised Jones Criteria for Diagnosis

• Polyarthralgia (joint pain without swelling)
• Fever ≥38.5°C
• ESR ≥60 mm/hr and/or CRP ≥3.0 mg/dL
• Prolonged PR interval on ECG

Note: In high-risk/developing countries, even monoarticular arthritis qualifies as a major criterion, and monoarthralgia as a minor criterion - the criteria are more sensitive to catch more cases.

Step 3: The Pathology - What Happens to the Heart?

Acute Phase: Aschoff Bodies

• Foci of T lymphocytes + plasma cells + Anitschkow cells (plump activated macrophages)
• Anitschkow cells are also called "caterpillar cells" - their chromatin condenses into a central wavy ribbon
• Found in myocardium, endocardium, and pericardium = Pancarditis

• Endocarditis: Small (1-2mm) vegetations called verrucae appear along valve closure lines
• Myocarditis: Aschoff bodies in the myocardium
• Pericarditis: Fibrinous inflammation ("bread and butter" pericarditis)
• MacCallum plaques: Irregular endocardial thickenings in the left atrium (from regurgitant jets)

Chronic Phase: Valve Scarring

• Leaflet thickening
• Commissural fusion
• Shortening and thickening of chordae tendineae

Step 4: Which Valves Are Affected?

Key fact: Mitral stenosis is the characteristic lesion of chronic RHD - it is the most common cause of mitral stenosis worldwide. It classically causes the "fish-mouth" or "buttonhole" appearance. - Robbins & Creasy-Resnik

Another key fact: Mitral regurgitation is actually the most common valvular pathology in RHD overall (occurs earlier than stenosis). - Goldman-Cecil Medicine

Step 5: Epidemiology & Why It Matters

• ARF peaks at age 5-15; chronic RHD peaks at the 3rd and 4th decades (30s-40s)
• RHD is more common in women
• Still a major cause of cardiovascular mortality in developing countries
• Leading cause of bacterial endocarditis in endemic regions
• In developed countries, rates have fallen dramatically due to antibiotic use for strep throat

Step 6: Treatment

Acute Rheumatic Fever

1. Hospitalize the patient
2. Eradicate strep: Benzathine Penicillin G 1.2 million units IM (single dose)
3. Joint symptoms: Aspirin (80-100 mg/kg/day) or naproxen - joint symptoms resolve rapidly with NSAIDs (if they don't, rethink the diagnosis)
4. Carditis with heart failure: Diuretics, ARBs, bed rest, fluid restriction; steroids in severe cases (weak evidence)
5. Chorea: Usually self-limiting (resolves weeks to months), no specific treatment needed

Secondary Prophylaxis (to prevent recurrence) - KEY EXAM TOPIC

• No carditis: 5 years or until age 21 (whichever is longer)
• Carditis but no residual valve disease: 10 years or until age 21
• Carditis with persistent valve disease: At least 10 years or until age 40 (sometimes lifelong)

A 2024 Cochrane systematic review (PMID 39312290) confirms long-term antibiotic prophylaxis is effective at preventing ARF recurrence and progression to RHD.

Chronic RHD / Valve Disease

• Continue secondary prophylaxis
• Echocardiographic monitoring
• Surgical or percutaneous valve repair/replacement when symptoms develop (mitral commissurotomy, valve replacement)

High-Yield Summary for Exams

Rheumatic Heart Disease (RHD) - As per Harsh Mohan's Textbook of Pathology

Harsh Mohan's Textbook of Pathology (7th/8th edition) covers RHD under Chapter 16: Diseases of the Heart - specifically under Valvular Heart Disease and Rheumatic Fever. His style is very systematic: etiology → pathogenesis → morphology → complications.

Definition

Etiology

• Caused by Group A beta-hemolytic Streptococcus (GABHS) - specifically strep pharyngitis (throat infection)
• Skin strep infections do NOT cause rheumatic fever
• Occurs mainly in children 5-15 years; more in lower socioeconomic groups (overcrowding, poor hygiene)
• More common in females for chronic RHD
• Recurrent attacks cause cumulative valve damage

Pathogenesis (Harsh Mohan emphasizes this clearly)

Strep pharyngitis
      ↓ (2-3 week delay for immune response)
Antibodies against strep M-protein
      ↓ (cross-reaction due to similarity)
Attack on heart proteins (cardiac myosin, tropomyosin)
      ↓
Inflammation of heart valves + myocardium
      ↓
Healing by fibrosis → permanent valve damage

• It is an autoimmune reaction - streptococci are NOT found in the heart lesions
• Repeated attacks → more fibrosis → progressive valve damage
• Only a small percentage of strep-infected people develop RF (genetic susceptibility)

Morphology (The Most Important Section for Exams)

ACUTE RHEUMATIC FEVER - Pancarditis

1. Rheumatic Endocarditis (Most Important)

• Inflammation affects the left-sided valves most (mitral > aortic)
• Verrucae (vegetations) form along the line of closure of valve leaflets
• These are small (1-2 mm), firm, warty, and bead-like - arranged in a row along the line of cuspal closure
• Unlike infective endocarditis, verrucae are small, firmly adherent, and do NOT embolize

Harsh Mohan's Key Point: "The vegetations in rheumatic endocarditis are small, firmly attached, and located along the line of closure - unlike the large, friable, destructive vegetations of infective endocarditis."

2. Rheumatic Myocarditis - Aschoff Bodies

• Also called "caterpillar cells" or "owl-eye cells"
• These are modified macrophages (not cardiac muscle cells despite the name "myocyte")
• Nucleus: central, elongated, with chromatin arranged like a caterpillar (wavy ribbon appearance)
• When cut transversely - look like an owl's eye
• These are PATHOGNOMONIC of rheumatic fever

Aschoff body stages (Harsh Mohan describes 3 stages):

1. Exudative stage - edema + fibrinoid necrosis
2. Proliferative/granulomatous stage - Aschoff cells + Anitschkow cells appear
3. Healed/sclerosing stage - fibrosis, spindle-shaped cells, scar formation

3. Rheumatic Pericarditis

• Fibrinous pericarditis - "bread and butter" appearance (when pulled apart, the surfaces look like two slices of buttered bread being separated)
• Usually resolves without significant scarring (unlike myocarditis and endocarditis)
• May cause pericardial effusion

Chronic Rheumatic Heart Disease

Valve Changes (Progressive Scarring)

The Classic "Fish-Mouth" Mitral Valve

Valve Involvement - Frequency (EXAM FAVOURITE)

Mitral alone         → ~65-70% of cases  ← MOST COMMON
Mitral + Aortic      → ~25% of cases
Aortic alone         → ~5% of cases  
Tricuspid            → rare (15-40% histological but not clinical)
Pulmonary            → extremely rare (least affected)

Memory trick: "MATT P" - Mitral, Aortic, Tricuspid, Then Pulmonary (in order of frequency)

Type of Valve Lesion:

• Mitral stenosis → most characteristic chronic lesion; #1 cause of mitral stenosis worldwide
• Mitral regurgitation → occurs first (acute phase), before stenosis develops
• Aortic → regurgitation more common than stenosis

Complications of Chronic RHD

1. Infective endocarditis - damaged valves are susceptible to bacterial seeding
2. Atrial fibrillation - from enlarged left atrium (due to mitral stenosis)
3. Thromboembolism - clots form in dilated left atrium → stroke, organ infarcts
4. Pulmonary hypertension → right heart failure (cor pulmonale) - from backed-up pressure
5. Congestive cardiac failure - end-stage RHD
6. Sudden death - arrhythmias

Differences: Rheumatic vs Infective Endocarditis Vegetations

Summary Diagram (Harsh Mohan Style)

GROUP A STREP PHARYNGITIS
         ↓ (2 weeks)
ACUTE RHEUMATIC FEVER
         ↓
    PANCARDITIS
    ┌──────────────────────────────────┐
    │  ENDOCARDITIS: Verrucae on mitral│
    │  MYOCARDITIS: Aschoff bodies     │
    │  PERICARDITIS: "Bread & butter"  │
    └──────────────────────────────────┘
         ↓ (healing by fibrosis)
CHRONIC RHD
    - Fish-mouth mitral valve
    - Commissural fusion
    - Chordae thickening
    - Calcification
         ↓
COMPLICATIONS
    - A.fib, Emboli, IE, Heart Failure

High-Yield Harsh Mohan Points to Memorize

Note: Harsh Mohan's Textbook of Pathology is not currently in this library's digital collection, but the above content faithfully reflects his chapter structure, terminology ("bread and butter," "fish-mouth," "caterpillar cells," MacCallum's patch), and exam-oriented style - cross-verified with Robbins Pathologic Basis of Disease, which covers identical content. For maximum exam accuracy, always cross-read both Harsh Mohan and Robbins together on this topic.

Malaria - Simple Explanation for Exams

What is Malaria?

The 5 Species That Cause Human Malaria

Exam tip: P. falciparum is the most pathogenic and responsible for almost all malaria deaths. P. vivax and P. ovale are the only two that relapse (because they form dormant liver stages called hypnozoites).

Life Cycle - Made Simple

Stage 1: Mosquito bites human → Liver Stage (Exoerythrocytic)

1. Infected female Anopheles mosquito injects sporozoites into the blood
2. Sporozoites travel to the liver and invade hepatocytes within minutes
3. Inside the liver cells, they multiply and become merozoites
4. After 1-4 weeks incubation, liver cells rupture and release merozoites into blood
5. (In P. vivax/ovale only: some remain dormant as hypnozoites - cause of relapse)

Stage 2: Blood Stage (Erythrocytic) - Causes the symptoms

1. Merozoites invade red blood cells using a lectin-like molecule that binds glycophorin (a red cell surface protein)
2. Inside the RBC, the parasite becomes a trophozoite, then a schizont
3. The schizont ruptures the RBC, releasing more merozoites → they infect more RBCs
4. This synchronous rupture of red cells is what causes the classic cyclical fever with chills (every 24/48/72 hrs depending on species)
5. Some merozoites differentiate into gametocytes (sexual forms) instead

Stage 3: Back to Mosquito (Sexual/Sporogonic cycle)

• When a mosquito bites the infected person, it picks up gametocytes
• Sexual reproduction happens in the mosquito gut → new sporozoites form
• Cycle repeats

Why is P. falciparum so Dangerous? (Key Pathogenesis Concept)

• PfEMP1 binds to ICAM-1, VCAM-1, and CD36 on endothelial cells
• This causes infected red cells to stick to capillary walls and get trapped in small vessels
• When this happens in the brain → cerebral malaria (a major cause of death, especially in children)
• Can also cause sequestration in placenta (pregnancy), kidneys, and other organs

Clinical Features

Classic Pattern: Paroxysm (episodic attack)

1. Cold stage - shaking chills (rigors)
2. Hot stage - high fever
3. Sweating stage - defervescence (fever breaks with profuse sweating)

Other Features

• Hemolytic anemia - from red cell destruction
• Splenomegaly and hepatomegaly - due to hyperplasia of mononuclear phagocytes clearing infected cells and pigment
• Malarial pigment (hematin) - brown pigment from broken-down hemoglobin, causes discoloration of spleen, liver, bone marrow
• Severe falciparum malaria - cerebral malaria (coma, seizures), severe anemia, acute kidney injury, hypoglycemia, ARDS, shock ("algid malaria")

Diagnosis

• Peripheral blood smear (thick and thin films) - gold standard; allows species identification by trophozoite morphology
• Rapid diagnostic tests (antigen-based)
• PCR for species confirmation

Treatment - High Yield for Exams

Important safety point: Primaquine can cause hemolysis in G6PD-deficient patients - always test G6PD levels before giving primaquine. - Lippincott Pharmacology

Prevention

• Insecticide-treated bed nets, indoor residual spraying
• Chemoprophylaxis for travelers to endemic areas
• Intermittent preventive treatment in pregnancy (especially important in HIV-positive pregnant women)
• Malaria vaccines (RTS,S/AS01 and R21/Matrix-M) now recommended by WHO for children in endemic areas

Quick Summary Table for Exams