What is the most likely diagnosis for a young female child who exhibits regression, does not speak, has decreased head size, and gait problems?

• A. Autism Spectrum Disorder
• B. Rett Syndrome
• C. Cerebral Palsy
• D. Down Syndrome

Answer: (B)

The symptoms described—regression, loss of speech, decreased head size, and gait problems—are characteristic of Rett Syndrome. This neurodevelopmental disorder primarily affects girls and typically becomes apparent after a period of normal development.

Rett Syndrome is caused by mutations in the MECP2 gene and leads to a distinctive pattern of developmental regression after the first few months to years of life. Affected children may initially develop skills and then lose them, particularly language and purposeful hand skills, and they often experience problems with movement and coordination, fitting the gait issues mentioned.

In addition to these signs, a notable feature of Rett Syndrome is a decrease in head circumference over time, which often indicates a loss of brain growth that contrasts with the initial development observed in the early months. This profile aligns well with the clinical presentation noted in the question.