# ICD-11 Classification of Rett Syndrome (LD90.0)

Canonical: https://pinnacleblooms.org/ask/what-is-the-icd-11-classification-for-rett-syndrome
Publisher: Pinnacle Blooms Network / Bharath Healthcare Laboratories Private Limited

In ICD-11-MMS, Rett syndrome is classified under code LD90.0 within developmental anomalies of the nervous system. It denotes a monogenic neurodevelopmental disorder, most often caused by MECP2 variants, marked by early normal development followed by regression of hand skills and language, gait abnormalities and stereotypic hand movements.

*When a girl presents with developmental regression after a period of normal early growth, the ICD-11 code clarifies the diagnosis with precision.*

## In short
Rett syndrome is classified in **ICD-11-MMS under code LD90.0**, sitting within the chapter on developmental anomalies (block *Developmental anomalies of the nervous system*). It denotes a distinct neurodevelopmental disorder, predominantly affecting girls and most commonly caused by pathogenic *MECP2* variants, characterised by a period of apparently normal early development followed by regression of acquired hand skills and spoken language, gait abnormalities, and the emergence of stereotypic hand movements.

## The classification, briefly
Under ICD-11, **LD90.0 Rett syndrome** is coded within the grouping of developmental anomalies of the nervous system rather than as a behavioural or intellectual-disability category — reflecting its recognised monogenic neurodevelopmental basis. This is a shift in emphasis from earlier classifications: ICD-11 treats Rett syndrome as a discrete clinical-genetic entity. Where intellectual or motor sequelae are relevant for the clinical picture, these may be captured with additional ICD-11 codes for associated functioning, in keeping with the linked ICF model of functioning and disability. Confirmation typically rests on the clinical course alongside *MECP2* molecular testing.

## When to refer
Any girl showing developmental regression — loss of acquired purposeful hand use, deceleration of head growth, emergence of midline hand stereotypies, or loss of spoken language after an initial period of typical development — warrants prompt paediatric neurology and genetic evaluation. Early identification supports timely *MECP2* testing, family genetic counselling, and a coordinated multidisciplinary therapy plan addressing communication, motor and self-care domains.

## The Pinnacle way
Developmental measurement supports care planning; diagnosis requires an appropriately qualified healthcare professional., under qualified clinician care — never from a code or an online form. Once the clinical picture is established, a coordinated plan spans [speech and communication therapy](https://www.pinnacleblooms.org/top-speech-therapy-center-india-proven-improvement-rate), [occupational therapy](https://www.pinnacleblooms.org/best-occupational-therapy-center-india-proven-improvement-rate) and movement support, with progress tracked using a structured, clinician-administered [AbilityScore® assessment](/ask/what-is-the-abilityscore-and-how-is-it-calculated).

## Trusted sources
WHO ICD-11 for Mortality and Morbidity Statistics (LD90.0, Rett syndrome); WHO International Classification of Functioning, Disability and Health (ICF) for capturing associated functioning.

**Next step —** Reviewing a child with developmental regression? [Partner with Pinnacle](/) for coordinated assessment and multidisciplinary therapy.

This is general information, not a diagnosis — individual assessment and diagnosis require an appropriately qualified healthcare professional.

## Sources
- WHO ICD-11 for Mortality and Morbidity Statistics: https://icd.who.int
- WHO International Classification of Functioning, Disability and Health (ICF): https://www.who.int

## Connected topics and perspectives
- Conditions: https://pinnacleblooms.org/ask/conditions
- Doctor: https://pinnacleblooms.org/ask/lens/stakeholder/doctor
- Context: https://pinnacleblooms.org/ask/lens/domain/context
- Definition: https://pinnacleblooms.org/ask/lens/intent/definition
- Screen: https://pinnacleblooms.org/ask/lens/lifecycle/screen
- Screen: https://pinnacleblooms.org/ask/lens/route/screen
- Early Clarity: https://pinnacleblooms.org/ask/lens/empowerment/early_clarity

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