A child with Group A strep infection is suspected to have rheumatic fever and develops involuntary movements. What is the likely diagnosis?

Involuntary movements in a child who has a recent Group A strep infection and is suspected to have rheumatic fever are indicative of Syndenham chorea. This condition is characterized by rapid, irregular, and unintentional movements, particularly affecting the limbs and face. It is considered a manifestation of rheumatic fever and occurs due to the autoimmune response triggered by the strep infection, where the immune system mistakenly attacks the basal ganglia in the brain.

Syndenham chorea often follows a streptococcal infection, particularly after pharyngeal infections, and is more common in children. This aligns with the context provided as the child has a Group A strep infection. In contrast, the other conditions listed do not typically develop from strep infections nor are they characterized by the same type of involuntary movements associated with rheumatic fever. Therefore, the distinct presentation of involuntary movements in this case strongly supports the diagnosis of Syndenham chorea linked to the underlying rheumatic fever.