Rheumatic Heart Disease (RHD)
Details of the Concept
Rheumatic heart disease is a long-term consequence of acute rheumatic fever, which arises from group A streptococcal pharyngeal infection. RHD results from an immune-mediated attack on cardiac valves through molecular mimicry — streptococcal antigens cross-react with valve endothelium proteins, triggering chronic valvular inflammation, fibrosis, and stenosis. RHD is the highest prevalent VHD in low-income countries and the most common cause of mitral stenosis worldwide.
Key Facts
Global Burden
- ~2.8 million incident cases and >40 million prevalent cases globally (GBD 2019); incident cases increased 1.5× and prevalent cases 1.7× from 1990–2019 sources/vhd-mechanism-aha-2024 (very high)
- Most common VHD in low-income countries; persists due to limited access to diagnostic resources and penicillin
- Invariably affects the mitral valve; aortic valve involved in 20–30% of cases
- RHD poses particular risks during pregnancy
Epidemiology and Demographics
- Female predominance: 80% of cases are women sources/vhd-mechanism-aha-2024 (very high)
- Left-sided predilection: mitral valve most affected; left-sided valves disproportionately involved vs right-sided — hypothesised mechanisms include greater pressure/shear stress, oxygen tension differences, physiological differences
- Highest burden in sub-Saharan Africa, South Asia, Oceania
Molecular Mechanisms
Step 1 — Streptococcal infection and molecular mimicry:
- Group A streptococcus (GAS) pharyngitis → linked CD4+ T-cell and B-cell reactivity to streptococcal antigens: M protein and group A carbohydrate epitope N-acetyl-b-D-glucosamine sources/vhd-mechanism-aha-2024 (very high)
- Autoantibodies produced that cross-react with valve endothelium proteins: laminin and cardiac myosin
- Lewis rat model supports mimicry hypothesis: immunisation with inactivated GAS or recombinant M5 protein → anti-myosin antibodies + valvular carditis
Step 2 — Valvular inflammation:
- Autoantibody binding → ↑VCAM-1 (vascular cell adhesion molecule 1) on valve surface → T-cell and macrophage infiltration into valve interstitium
- Early phase dominated by proinflammatory cytokines from T cells and macrophages: IFN-γ, IL-17, TNF-α
Step 3 — Chronic fibrosis:
- Chronic inflammation → valve fibrosis driven by canonical fibrotic mediator TGF-β
- Progressive scarring leads to mitral stenosis or regurgitation
Complement pathway:
- FCN1, FCN2, FCN3 (ficolins): pattern recognition receptors binding lipoteichoic acid and other GAS cell wall components → activation of mannose-binding lectin (MBL) pathway of complement
- MBL2 also a susceptibility locus — consistent with complement pathway involvement in early valvular damage sources/vhd-mechanism-aha-2024 (very high)
ProTα (prothymosin-α) — sex predilection mechanism:
- Newly identified in RHD pathogenesis; contributes to CD8+ T-cell cytotoxicity associated with estrogen receptor α activity
- ProTα facilitates CD8+ T-cell recognition of human type I collagen (shows molecular mimicry with Streptococcus pyogenes)
- Proposed as mechanism for female sex predilection in RHD sources/vhd-mechanism-aha-2024 (very high)
Genetics
- HLA class II MHC risk alleles: identified by GWAS; specific alleles vary by population sources/vhd-mechanism-aha-2024 (very high)
- Other susceptibility loci: CTLA4 (T-cell regulation), FCGR2A, FCN1, FCN2, FCN3, IGH, IL10, IL1RN, MBL2, TLR2, TNF, TGFB1
- RHDGen Network study (n=2,548 RHD patients, 8 African countries): replicated IGH locus; novel susceptibility locus on chromosome 11 exclusive to Black African individuals
Clinical Manifestations
- Mitral stenosis (most common long-term consequence); mitral regurgitation; combined MV disease
- Aortic valve involvement in 20–30%
- Right-sided involvement less common
- Progressive worsening over years; acute decompensation during pregnancy or intercurrent illness
Treatment
Prevention and primary treatment:
- Penicillin for acute GAS infection; secondary prophylaxis with penicillin is critical sources/vhd-mechanism-aha-2024 (very high)
- Secondary prophylaxis effective if maintained long-term; adherence is a major barrier
Current supportive care:
- NSAIDs, corticosteroids, IVIG for acute rheumatic fever — meta-analyses do NOT support benefit on valve outcomes
- HF from chronic RHD: diuretics, fluid restriction, ACE inhibitors
- Valve replacement surgery (definitive intervention for severe disease)
Emerging/investigational:
- Biologics targeting: T-cell activation, proinflammatory cytokines (IFN-γ, IL-17, TNF), cell adhesion molecules (VCAM-1), complement activation — theoretically applicable based on immunopathogenesis
- Major barrier: cost, distribution, storage, and administration of biologics in resource-limited settings where RHD is most prevalent
- Dapagliflozin trial in severe mitral stenosis (Dapa-Rhemis, NCT05618223, n=36) — endpoints: mitral valve mean pressure gradient, KCCQ sources/vhd-mechanism-aha-2024 (very high)
Contradictions / Open Questions
- Why is RHD 2× more prevalent in women? ProTα/estrogen receptor α hypothesis proposed but not confirmed sources/vhd-mechanism-aha-2024 (very high)
- Why are left-sided heart valves disproportionately affected? Hypothesised: higher pressure, shear stress, oxygen tension — not experimentally confirmed
- Whether GAS vaccine development could substantially reduce RHD burden remains a major global health priority
- The Lewis rat model is the predominant animal model but rat genetic tools are limited; K/BxN mouse model (autoantibody-dependent arthritis) increasingly used to dissect immunopathogenic mechanisms
Connections
- Related to concepts/Mitral-Stenosis — RHD is the most common cause of mitral stenosis worldwide
- Related to concepts/Valvular-Heart-Disease — VHD clinical overview
- Related to entities/Mitral-Valve-Prolapse — alternative cause of primary mitral valve disease
- Related to concepts/CAVD-Mechanisms — comparison: CAVD is mechanistically driven by lipid/calcific vs RHD by immune-mediated mechanisms
- Related to sources/vhd-mechanism-aha-2024