F84.2

HCC Category Mapping

What This Code Means

A rare genetic disorder where a child develops normally for the first 6-18 months, then loses previously acquired skills in language, motor function, and social abilities.

Coding Tips

• •Confirm the diagnosis is Rett syndrome specifically, as it has distinct diagnostic criteria including normal development followed by regression
• •Code the associated seizures separately if present (G40 codes)

Clinical Significance

Rett syndrome is a rare genetic neurodevelopmental disorder caused predominantly by mutations in the MECP2 gene, affecting primarily females. It is characterized by normal early development followed by regression of language and purposeful hand skills, development of stereotypic hand movements, and gait abnormalities. Patients require lifelong multidisciplinary care for seizures, scoliosis, breathing irregularities, and nutritional challenges.

Documentation Requirements

• ✓Provider documentation of Rett syndrome diagnosis, ideally with genetic confirmation (MECP2 mutation)
• ✓Documentation of developmental regression following a period of normal early development
• ✓Evidence of characteristic features: loss of purposeful hand skills, stereotypic hand movements, gait abnormalities
• ✓Assessment of current functional status including communication, mobility, and feeding
• ✓Documentation of comorbid conditions (epilepsy, scoliosis, breathing abnormalities) and current management

Commonly Confused Codes