Assessment of Disease Activity
The activity of the rheumatic process is assessed by two key morphological criteria. First is the presence of specific Aschoff bodies (rheumatic granulomas). Second is the development of nonspecific exudative, as well as exudative-proliferative, reactions.
Such nonspecific changes are localized predominantly in cardiac tissues and the interstitium of various internal organs. The cellular infiltrate consists mainly of lymphocytes and macrophages, occasionally admixed with eosinophils and neutrophils. Additionally, vasculitis consistently arises within the microvasculature.
Main Forms of Rheumatic Fever
Four main forms of the disease are distinguished:
- Cardiovascular form. Develops significantly more often than the others. Its mandatory component is rheumatic endocarditis. If inflammation encompasses both the endocardium and myocardium, rheumatic carditis is diagnosed. When there is combined involvement of absolutely all layers of the heart—endocardium, myocardium, and pericardium—it is termed rheumatic pancarditis.
- Polyarthritic form. Characterized by large joint involvement. Foci of connective tissue disorganization form in the synovial membrane, and synovitis develops. Vasculitis occurs, accompanied by pronounced hyperemia, while lymphoid infiltrates accumulate around vessels forming cuff-like structures. Serous or serous-fibrinoid effusion forms in the joint cavity. A crucial feature of this form is that the articular cartilage is not involved in the pathological process, so joint deformities never occur.
- Nodular form. Manifests as the formation of specific subcutaneous nodules and papules. Most frequently, they are localized on the extensor surfaces of large joints, along the spine, as well as in fasciae, tendons, and aponeuroses. Microscopically, such a nodule represents a focus of fibrinoid necrosis densely surrounded by a cellular infiltrate of macrophages and lymphocytes. Over time, small scars form at the site of these nodules. This form typically proceeds against the background of simultaneous heart involvement.
- Cerebral form (Sydenham's chorea). Distinguished by primary brain involvement. Morphologically, it manifests as arteritis, the formation of microglial nodules, and dystrophic changes in nerve cells. In rare cases, focal hemorrhages are possible. Notably, involvement of other systems and organs in Sydenham's chorea is poorly expressed.
Rheumatic Vasculitis
Involvement of the vascular bed in rheumatic fever is generalized and detected almost constantly. The primary targets are the vessels of the microcirculation.
- In arteries and arterioles, fibrinoid changes develop, frequently complicated by thrombosis.
- In capillaries, active proliferation followed by desquamation of endothelial cells is observed—a process termed rheumatic endotheliosis. Concurrently, peculiar cuffs formed by proliferating adventitial cells develop around the capillaries.
The regular outcome of such vasculitis is sclerosis of the vascular wall, leading to the development of arteriosclerosis, arteriolosclerosis, and capillarosclerosis.
Complications and Outcomes
During an acute rheumatic attack, absolutely all organs and body systems may be drawn into the pathological process. Severe complications include superimposed infective endocarditis, rheumatic pneumonia, focal or diffuse glomerulonephritis, and polyserositis.
Extracardiac manifestations are quite diverse:
- Serous membranes: adhesion formation in the pleural, pericardial, and peritoneal cavities.
- Skeletal muscles: appearance of foci of waxy (Zenker's) necrosis.
- Skin: rash and erythema marginatum.
- Endocrine system: dystrophic and atrophic changes in glands.
- Vessels: development of thromboembolic syndrome.
The outcomes of the disease are inextricably linked to the severity of cardiovascular system involvement. Directly during the rheumatic attack, there is a serious threat of acute cardiovascular failure and fatal arrhythmias. In the long term, established valve defects and cardiosclerosis inevitably lead to progressive chronic heart failure.