Early-Onset Rheumatic Carditis in a Four-Year-Old: Diagnostic and Immunologic Insights.

Rheumatic fever (RF) is an autoimmune inflammatory disease that occurs several weeks after an episode of pharyngitis caused by Group A β-hemolytic Streptococcus. Rheumatic heart disease (RHD) is a direct consequence of cardiac inflammation and develops through autoimmune mechanisms, including molecular mimicry between streptococcal antigens and host cardiac proteins. Although its global incidence has declined, RF remains endemic in certain regions, and sporadic cases continue to occur in Europe.  We report the case of a three-year-eight-month-old girl presenting with acute behavioral changes and generalized choreiform movements, without preceding infectious symptoms. Elevated anti-streptolysin O titers supported recent streptococcal exposure. Initial echocardiography revealed trivial mitral and aortic regurgitation despite the absence of a murmur; however, serial examinations showed rapid progression to significant regurgitation of both valves. Treatment included oral penicillin, corticosteroids, sodium valproate, and initiation of secondary prophylaxis. Chorea completely resolved within one month. At the 10-month follow-up, aortic regurgitation had resolved, and mitral regurgitation markedly improved. This case illustrates the diagnostic importance of serial echocardiography in detecting evolving subclinical carditis in patients presenting with Sydenham's chorea. Although young age is associated with a higher risk of progression, valvular lesions may regress with appropriate therapy and prevention of recurrence. RF should be considered in choreiform presentations even at very young ages. Early evaluation, repeated echocardiography, and adherence to long-term secondary prophylaxis are essential for preventing disease progression.