Rheumatic Fever & Rheumatic Heart Disease
Introduction, Etiology, Pathophysiology and Clinical Manifestation
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Introduction to Rheumatic Fever
Rheumatic fever is multisystem, immune mediated, non suppurative acute inflammation which develops after streptococcal sore throat. Immune response may not be extremely specific and may cross react with our own tissue producing inflammation in CNS, heart tissue, synovial membrane of joints, skin and subcutaneous tissue. The cytokines produced during inflammation precipitate the fever. Whenever these patients acquire that specific type of sore throat, they have tendency to develop rheumatic fever. Peak incidence of this disease is between 5-15 years of age. It has following characteristics:
Multiple system in body are inflamed
Immune mediated inflammation
Bacteria are never found in these tissues
Etiology of Rheumatic Fever
What are Special Streptococcal (Group A Streptococcal) Infections?
The bacterium is rheumatogenic strain of Streptococcus, Beta hemolytic, Lancefield group A.
Some of the streptococcal capsular antigens are similar with glycoprotein in cardiac valves. So when immune system reacts against bacterial antigens, it may cross react with the cardiac glycoprotein. Another theory claims that protein M of bacterial cell membrane is very similar to protein in sarcolemma of myocardial cells.
Streptococcal Sore Throat and Reaction of Immune System
In 97% cases when a person suffers with streptococcal sore throat, immune system activates and eliminates the bacteria. In 2-3% genetically predisposed cases, immune system cross react with our own tissue because of antigenic mimicry. It may attack and produce inflammatory lesions in cardiac tissue, joints, skin, subcutaneous tissue and CNS.
Pathophysiology: Complications of Rheumatic Fever
CNS involvement in Rheumatic Fever
During rheumatic fever immune system cross react with CNS and produces inflammation of basal ganglia. Suddenly, the patients develop chorea which is purposeless, involuntary, jerky movements of the limbs. In some patients chorea develops during fever whether in others chorea develops after few months. Chorea is a major diagnostic feature of rheumatic fever. Other terms for this chorea are Sydenham chorea, rheumatic chorea or Saint Vitus dance. Chorea is more common in girls and does not produce long term residual damage to the CNS.
Clinical Manifestation of Rheumatic Fever
In the patients with streptococcal sore throat, immune system can cross react with synovial membranes of multiple joints and these patients may develop arthritis or arthralgia. These patients develop severely painful migratory polyarthritis which show good response to Aspirin and /or salicylates. Once the fever is over, joints will be as normal as possible. No long term complications are noticed in the joints.
Difference Between Arthritis and Arthralgia
Arthritis is one of the major criteria to diagnose the rheumatic fever. The severe inflammation causes painful, tender and swollen joints.
Arthralgia is one of the minor criteria to diagnose the disease. Patients complain pain in joints but there is neither tenderness nor swelling.
One of the clinical features of rheumatic fever is erythema marginatum. Some of skin antigens are also similar with the bacterial antigen so immune system may cross react with the skin. So on the skin appear rapidly enlarging erythematous macules while the central area starts healing. These are usually painless and more commonly present on the trunk. No long term complications are noticed on the skin.
Subcutaneous Tissue Involvement in Rheumatic Fever
In rheumatic fever, immune system cross react with the connective tissue of subcutaneous area. This will lead to formation of non tender, ½ to 1 cm nodules usually under bony prominences on the extensor surfaces of the limbs and are attached with synovial sheets of the tendons. They do not produce long term complications.
Rheumatic Fever Causing Cardiac Problems
During acute phase of rheumatic fever immune system also react with cardiac tissue. Rheumatic fever may involve pericardium, myocardium, endocardium and produces rheumatic pericarditis, rheumatic myocarditis and rheumatic endocarditis respectively. If all three tissues are involved then this is termed as rheumatic pancarditis.
Rheumatic Heart Disease
All the cardiac problems present during the rheumatic fever are called rheumatic heart disease. It may be rheumatic pericarditis, rheumatic myocarditis or rheumatic endocarditis.
Fibrous pericarditis is feature of any immune mediated pericardial inflammation. In rheumatic fever, fibrinogen shifts from vascular compartment to pericardial sac. If layers of pericardium are separated then deposited fibrin appears as bread and butter, that’s why this is called bread and butter pericarditis. Once the fever is resolved, the fibrin is reabsorbed after cut down by plasmin. Rheumatic pericarditis does not have long term complications.
Myocarditis developing during acute fever is most dangerous complication of rheumatic fever. Myocardium becomes loose and flabby. It may lead to CCF (congestive cardiac failure). Children develop more sever clinical features of RVF then LVF. If baby survive this feature then no long term complications are reported with rheumatic
In rheumatic fever there are immune mediated granulomas present in myocardial tissue. These granulomas are especially present around the perivascular connective tissue and are surrounded by collagen fibers, plasma cells, neutrophils and special type of macrophages (with prominent nucleus having ribbon like chromatin).
The macrophages (with prominent nucleus and ribbon like chromatin) present within granulomas characteristically in rheumatic myocarditis are called anitschkow cells.
Aschoff Giant Cells
These large macrophages (Anitschkow cells) come together and form multinucleated aschoff giant cells.
During rheumatic fever, immune system specially attack on endocardium lining the valves and produce rheumatic valvulitis.
These are multiple small vegetations consisting of fibrin and platelets along the line of closure of valves. These sterile vegetations are held their tightly and do not embolize. When fever is over these vegetations heals but platelets from these vegetations release platelet derived growth factor. Lot of fibroblasts get activated there and lay down collagen. Valvular leaflets may develop some adhesions due to this collagenization. When fever is over, these vegetations heal by fibrosis and valve becomes fibrotic and distorted. During every Rheumatic fever attack, this person develops accumulative pathological distortions of valve.
Chronic Rheumatic Heart Disease
In the long run when patient develop valvular lesions which lead to progressive valvular deformities, it is called chronic rheumatic heart disease. Every rheumatic fever episode leads to fibrosis, distortions, adhesions and calcifications in the valves. Due to repeated attacks of rheumatic fever, valvular lesions have accumulative damage and eventually at the age to 15-20 years children will develop severe valvular lesions like mitral stenosis /regurgitation or aortic stenosis /regurgitation.