Rett syndrome

What it is, and who it affects

Rett's syndrome is inherited in X-linked dominant fashion.

On who is affected the two pages differ in force: one says it only affects females, the other that Rett's disorder occurs almost exclusively in girls.

Normal, then losing it back

In the first 5 months of age the child has normal psychomotor development and normal head circumference. This is followed by deceleration of head growth between the age of 5 months and 4 years. The acquired skills (motor and language) are progressively lost.

Development stays relatively normal until 6-18 months of age, after which many of the symptoms common to autism appear; the 5-month mark is where head growth starts to slow, inside that normal period.

The MCQ picture: a 3-year-old girl is clumsy with poorly coordinated movement, her language is impaired and she wrings her hands constantly, and her head is smaller in comparison with the rest of her body. The answer is Rett's disorder, against Asperger's disorder, Down syndrome, congenital rubella and childhood disintegrative disorder.