Sudden onset of tics, obsessive-compulsive symptoms in a child after Scarlet fever is due to
**Core Concept**
Post-streptococcal autoimmune reactions can lead to the development of neuropsychiatric symptoms, including tics and obsessive-compulsive disorder (OCD), following a streptococcal infection such as Scarlet fever. This phenomenon is known as post-streptococcal neuropsychiatric disorders (PSND).
**Why the Correct Answer is Right**
The correct answer is associated with the development of antibodies against basal ganglia and other brain regions, leading to inflammation and damage. This is thought to be mediated by molecular mimicry between streptococcal antigens and brain tissue antigens. The resulting autoimmune reaction can cause a range of neuropsychiatric symptoms, including tics, OCD, and attention deficit hyperactivity disorder (ADHD).
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specifically relate to the development of neuropsychiatric symptoms after Scarlet fever.
**Option B:** This option is incorrect because it does not accurately describe the underlying mechanism of post-streptococcal neuropsychiatric disorders.
**Option C:** This option is incorrect because it is not a recognized cause of neuropsychiatric symptoms following Scarlet fever.
**Clinical Pearl / High-Yield Fact**
It's essential to consider post-streptococcal neuropsychiatric disorders in children who develop tics, OCD, or other neuropsychiatric symptoms following a streptococcal infection. This can help guide diagnosis and treatment, which may involve antibiotics, anti-inflammatory medications, and psychiatric interventions.
**Correct Answer: D, Sydenham's chorea is a type of post-streptococcal neuropsychiatric disorder.**