Question

An infant girl shows normal early development followed by regression of acquired milestones at around 6-18 months, with deceleration of head growth and loss of purposeful hand use replaced by stereotyped hand-wringing movements. The most likely diagnosis is:

• A. Rett syndrome
• B. Childhood disintegrative disorder (Heller syndrome)
• C. Classic autism spectrum disorder
• D. Attention-deficit/hyperactivity disorder

Hint:

Girl, early regression, shrinking head, hand-wringing - think MECP2.

Answer 1

The Correct Option is A

Step 1: Key feature is regression of milestones beginning early (around 6-18 months) after a period of normal development, in a girl.

Step 2: This points to Rett syndrome, an X-linked neurodevelopmental disorder (MECP2 mutation) seen almost exclusively in girls. Hallmarks: deceleration of head growth (acquired microcephaly), loss of purposeful hand skills with stereotyped hand-wringing/washing movements, gait abnormalities and loss of language.

Step 3: Timing is the discriminator. Childhood disintegrative disorder (Heller syndrome) shows normal development for at least 2 years (usually >3-4 years) before a marked regression - consistent with the examiner's own note ">2 yrs / Heller". Regression as early as 6 months therefore favours Rett, not Heller.

Step 4: Why the others are wrong - classic autism involves persistent social-communication deficits without the characteristic acquired microcephaly and hand-wringing of Rett; ADHD is a disorder of attention/hyperactivity with no milestone regression.

Key fact: Early regression + acquired microcephaly + hand-wringing stereotypies in a girl = Rett syndrome; late regression (>2 yrs) = Heller/childhood disintegrative disorder.