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Rett Syndrome: ICD-11 Definition and Early Childhood Features
Rett syndrome (ICD-11 LD90.0) is a neurodevelopmental disorder, usually from MECP2 variants and predominantly affecting females, marked by normal early development followed by regression with loss of purposeful hand use and language, stereotypic midline hand movements, gait abnormality and head-growth deceleration. Seizures and autonomic features are common, warranting prompt neurology referral.
In this answer 4 sections
A girl with normal early milestones who then plateaus and loses purposeful hand use — that clinical arc is the signature of Rett syndrome.
In short
Rett syndrome (ICD-11 LD90.0) is a neurodevelopmental disorder, in most classic cases caused by pathogenic MECP2 variants, affecting predominantly females. It is characterised by a period of apparently normal early development followed by regression, with loss of acquired purposeful hand skills and spoken language, gait abnormalities, and the emergence of stereotypic midline hand movements. It is a clinically and genetically defined condition — not a therapy-first label.
The science, briefly
The ICD-11 framing reflects the recognised natural history. After largely typical development through roughly 6–18 months, early childhood features include:
- Regression — loss of previously acquired purposeful hand use and expressive language
- Hand stereotypies — characteristic midline wringing, washing, clapping or mouthing movements
- Gait and motor abnormalities — apraxia, truncal ataxia, or loss of ambulation
- Deceleration of head growth (acquired microcephaly in classic presentations)
- Frequently associated features: breathing irregularities when awake, bruxism, seizures, autonomic dysfunction and disrupted sleep
Genetic confirmation (MECP2) supports classic Rett; atypical variants involve CDKL5 and FOXG1. Because seizures and autonomic involvement are common, this warrants prompt paediatric neurology referral alongside developmental support.
The Pinnacle way
Developmental measurement supports care planning; diagnosis requires an appropriately qualified healthcare professional., under qualified clinician care — never from an app or online form. For confirmed cases we coordinate multidisciplinary support spanning Rett syndrome care, occupational therapy for hand function and posture, and a baseline via the clinician-administered AbilityScore®.
Trusted sources
WHO ICD-11 (LD90.0); WHO ICF functioning framework; consensus diagnostic criteria for Rett syndrome.
Next step — For a child showing developmental regression or hand stereotypies, expedite neurology referral and partner with Pinnacle for coordinated developmental support.
This is general information, not a diagnosis — individual assessment and diagnosis require an appropriately qualified healthcare professional.
CONNECT THE ANSWER TO YOUR CHILD’S DAY
Something to notice. Something to discuss.
What to notice
Regression after normal early development: loss of purposeful hand use and spoken language, emergence of midline hand stereotypies, gait apraxia or ataxia, deceleration of head growth, and waking breathing irregularities.
In everyday life
Document the timeline of acquired-then-lost skills precisely — the regression arc is the most diagnostically useful history and guides genetic and neurology referral.
Bring your observations and questions to your child’s professional. Choose activities that suit your child’s comfort, abilities and agreed plan.
Bring your questions to a first visitQuestions families ask
What is the ICD-11 code for Rett syndrome?
Rett syndrome is classified under ICD-11-MMS code LD90.0 as a neurodevelopmental disorder with characteristic regression and hand stereotypies.
Which gene is most associated with classic Rett syndrome?
Most classic cases are caused by pathogenic variants in the MECP2 gene. Atypical presentations may involve CDKL5 or FOXG1.
How early can Rett syndrome features appear?
Early development is typically normal until around 6–18 months, after which regression, loss of purposeful hand use and characteristic midline hand stereotypies emerge.
Does Rett syndrome require neurology referral?
Yes. Because seizures and autonomic dysfunction are common, prompt paediatric neurology referral is warranted alongside multidisciplinary developmental support.
FOLLOW THE SOURCE
References behind this answer.
- Organisation website · further readingWHO ICD-11 — Rett syndrome (LD90.0)
- Organisation website · further readingWHO — neurodevelopmental disorders overview
References are supplied with this answer. An organisation homepage offers further reading; it does not establish an independent review of this page.
Content attribution: SETU Consortium · Pinnacle Blooms Network.
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