RHEUMATIC Essays - Medicine, RTT, Clinical Medicine, Health

RHEUMATIC Essays - Medicine, RTT, Clinical Medicine, Health RHEUMATIC FEVER Neelakantan Viswanathan It is an acute inflammatory disease of children and young adults caused by infection with pharyngeal strains of Group A beta haemolytic streptococci (serotypes 3,5,18,24). It is not due to a direct infection or toxin production but due to an autoimmune reaction triggered by molecular mimicry between the M proteins of the infecting Streptococcus pyogenes and cardiac myosin and the sarcolemmal membrane protein, laminin. During active carditis, helper CD4 lymphocytes increase in number and the ratio of CD4 to CD8 cells increase in the heart valves and peripheral blood. All patients with acute rheumatic fever demonstrate a non-HLA alloantigen which is expressed on the B cells (D8/17). HLA DR1,2,3,4,7 and 53 have also been linked to acute rheumatic fever. The mean age of onset is 5-15 years being prevalent in the developing world and is rare in Europe and North America. The time taken for rheumatic fever to develop after an attack of streptococcal pharyngitis is about 2 weeks. It is said to" lick" the joints but "bite" the heart. The other organs affected are the central nervous system and the skin. Overcrowding and poor sanitation may augment the spread amongst people. Valvular heart disease that is chronic and progressive is the end result in about 50 % of those affected. There is no gender predilection but mitral stenosis and chorea occur more commonly in females. About 1.5 million people have rheumatic heart disease in India but the incidence is declining nowadays due to improvement in sanitation. It is a pancarditis affecting all layers of the heart.The characteristic lesion is the Aschoff nodule, composed of multinucleated giant cells, having elongated nuclei with distinct chromatin pattern, surrounded by macrophages and T lymphocytes,occurring in the subendocardium of the left ventricle, and consists of a granulomatous lesion with an area of central fibrinoid necrosis. Anichkov's myocytes are cells containing these elongated "caterpillar" or "owl- eye" nuclei. Mac Callum's patch in the left atrial wall above the posterior mitral valve leaflet, which is thick and rough, is a predisposing lesion for infective endocarditis, where vegetations form. Small vegetations may occur on the endocardium (on the valves) and valvular regurgitation results to a certain degree. A serofibrinous effusion may occur in the pericardium. During the acute inflammation, subcutaneous nodules and synovitis occur. The large joints are affected as opposed to predominant small joints involvement in rheumatoid arthritis. Diagnosis of acute rheumatic fever is based on revised Duckett Jones criteria (1992) which requires the presence of at least two major or one major with two minor criteria to make a diagnosis, associated with evidence of a preceding streptococcal infection. MAJOR CRITERIA: 1. Carditis 2. Polyarthritis 3. Subcutaneous nodules 4. Erythema marginatum 5. Chorea MINOR CRITERIA: 1. Arthralgia 2. Fever 3. Leucocytosis 4. Elevated ESR and/or C-reactive protein 5. Prolonged PR interval in electrocardiogram ( First degree heart block) 6. Previous rheumatic fever EVIDENCE OF PRECEDING STREPTOCOCCAL INFECTION: A history of recent scarlet fever or ASLO titre (anti-stretolysin O titre > 250 Todd units in adults and > 333 in children or a positive rapid streptococcal antigen test. Other streptococcal antibodies are anti- hyaluronidase , anti- DNase and anti-streptokinase or a positive Streptozyme test. Throat cultures, if positive , for streptococci would be ideal. In this part of the world, we encounter many other manifestations of rheumatic fever as 1.Rheumatic pneumonia or pleural effusions 2.Abdominal pain (due to mesenteric adenitis commonly) 3.Epistaxis ( recurrent) Clinical features: CARDITIS : is classically a pancarditis characterized by pericarditis, myocarditis and endocarditis.It may be manifested by chest pain, pericardial rub and effusion , tachycardia out of proportion to fever , muffled heart sounds, gallop, low cardiac output and rarely syncope. Cardiomegaly and a "mushy" quality of the first heart sound are also encountered. Endocarditis is characterized by fever and changing murmurs. A murmur of mitral regurgitation is the most common while Carey Coombs murmur ( mid diastolic murmur at the apex) due to acute rheumatic valvulitis and a murmur of aortic regurgitation may also occur. Congestive heart failure with hepatic congestion are recognized features. Echocardiographically, since the left ventricular systolic function is preserved the cardiac failure is due to valve dilatation and not due to myocarditis. ST-T wave changes, reduction in QRS voltages, first degree AV block and other conduction defects may feature in the electrocardiogram . SUBCUTANEOUS NODULES: usually occur over bony prominences as olecranon, external occipital protuberance and vertebral bodies.They measure 0.5-2 cm in size. They go hand in hand with carditis and are firm and painless. They may also occur over joints and tendons. They have a histological pattern resembling Aschoff nodules. ARTHRITIS: is classically a polyarthritis which is