{"h1":"ICD-11 Classification of Rett Syndrome (LD90.0)","faq":[{"a":"Rett syndrome is coded LD90.0 in ICD-11-MMS, within the block of developmental anomalies of the nervous system.","q":"What is the ICD-11 code for Rett syndrome?"},{"a":"ICD-11 recognises Rett syndrome as a discrete monogenic neurodevelopmental entity, most often linked to MECP2 variants. Associated intellectual or motor functioning can be captured with additional ICD-11 codes alongside LD90.0.","q":"Why is Rett syndrome classified as a developmental anomaly rather than an intellectual disability?"},{"a":"Diagnosis rests on the characteristic clinical course of regression after early typical development, supported by MECP2 molecular genetic testing. Assessment must be conducted by qualified clinicians.","q":"How is Rett syndrome confirmed?"}],"lang":"en","slug":"what-is-the-icd-11-classification-for-rett-syndrome","title":"ICD-11 Classification of Rett Syndrome (LD90.0)","entity":{"key":"rett","kind":"condition","name":"Rett Syndrome","slug":null},"lenses":[{"kind":"stakeholder","label":"Doctor","value":"doctor"},{"kind":"domain","label":"Context","value":"context"},{"kind":"intent","label":"Definition","value":"definition"},{"kind":"lifecycle","label":"Screen","value":"screen"},{"kind":"route","label":"Screen","value":"screen"},{"kind":"empowerment","label":"Early Clarity","value":"early_clarity"}],"parent":{"key":"conditions","label":"Conditions"},"related":[{"lang":"en","slug":"what-is-the-icd-11-classification-for-genetic-chromosomal-syndromes","title":"What is the ICD-11 classification for Genetic / Chromosomal Syndromes?"},{"lang":"en","slug":"what-is-the-icd-11-classification-for-down-syndrome","title":"ICD-11 Classification for Down Syndrome (LD40.0)"},{"lang":"en","slug":"what-is-genetic-chromosomal-syndromes-and-what-are-its-icd-11-features-in-early-childhood","title":"Genetic / Chromosomal Syndromes: ICD-11 Features in Early Childhood"},{"lang":"en","slug":"what-is-the-icd-11-classification-for-intellectual-disability","title":"ICD-11 Classification for Intellectual Disability (6A00)"},{"lang":"en","slug":"what-is-the-icd-11-classification-for-developmental-language-disorder","title":"ICD-11 Classification for Developmental Language Disorder"},{"lang":"en","slug":"what-is-the-icd-11-classification-for-autism-spectrum","title":"What is the ICD-11 classification for Autism Spectrum?"}],"summary":"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.","answer_md":"*When a girl presents with developmental regression after a period of normal early growth, the ICD-11 code clarifies the diagnosis with precision.*\n\n## In short\nRett 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.\n\n## The classification, briefly\nUnder 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.\n\n## When to refer\nAny 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.\n\n## The Pinnacle way\nDevelopmental 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).\n\n## Trusted sources\nWHO ICD-11 for Mortality and Morbidity Statistics (LD90.0, Rett syndrome); WHO International Classification of Functioning, Disability and Health (ICF) for capturing associated functioning.\n\n**Next step —** Reviewing a child with developmental regression? [Partner with Pinnacle](/) for coordinated assessment and multidisciplinary therapy.\n\nThis is general information, not a diagnosis — individual assessment and diagnosis require an appropriately qualified healthcare professional.","canonical":"https://pinnacleblooms.org/ask/what-is-the-icd-11-classification-for-rett-syndrome","editorial":{"reviewed_at":"2026-06-11T20:12:18.613642+00:00","reviewed_by":null,"developed_by":"SETU Consortium · Pinnacle Blooms Network"},"alternates":[{"href":"https://pinnacleblooms.org/ask/what-is-the-icd-11-classification-for-rett-syndrome","lang":"en","indexable":true},{"href":"https://pinnacleblooms.org/ask/what-is-the-icd-11-classification-for-rett-syndrome-te","lang":"te","indexable":true}],"dimensions":[{"key":"conditions","label":"Conditions"}],"meta_title":"Rett Syndrome ICD-11 Classification (LD90.0)","meta_robots":"index, follow, max-image-preview:large","everyday_tip":"Document the timeline of skill loss precisely — age of regression onset and which skills were lost guides MECP2 testing and differential diagnosis.","published_at":"2026-06-10T10:52:00.07543+00:00","reading_paths":[{"key":"understand","items":[{"lang":"en","slug":"what-is-the-icd-11-classification-for-autism-spectrum","title":"What is the ICD-11 classification for Autism Spectrum?","reason":"Linked from this answer"},{"lang":"en","slug":"what-is-the-icd-11-classification-for-down-syndrome","title":"ICD-11 Classification for Down Syndrome (LD40.0)","reason":"Linked from this answer"},{"lang":"en","slug":"what-is-the-icd-11-classification-for-genetic-chromosomal-syndromes","title":"What is the ICD-11 classification for Genetic / Chromosomal Syndromes?","reason":"Linked from this answer"},{"lang":"en","slug":"what-is-the-icd-11-classification-for-developmental-language-disorder","title":"ICD-11 Classification for Developmental Language Disorder","reason":"Linked from this 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Diagnostic Pathway in Children Under 7","reason":"Same topic"},{"lang":"en","slug":"how-does-abilityscore-track-progress-in-a-child-with-rett-syndrome","title":"How AbilityScore Tracks Progress in a Child with Rett Syndrome","reason":"Same topic"},{"lang":"en","slug":"how-is-rett-syndrome-assessed-in-a-young-child","title":"How Rett Syndrome Is Assessed in a Young Child","reason":"Same topic"},{"lang":"en","slug":"how-is-rett-syndrome-assessed-in-children-under-7","title":"How Rett Syndrome Is Assessed in Children Under 7","reason":"Same topic"},{"lang":"en","slug":"what-does-an-abilityscore-of-0-100-mean-for-a-child-with-rett-syndrome","title":"What an AbilityScore® of 0–100 means for a child with Rett Syndrome","reason":"Same topic"},{"lang":"en","slug":"what-does-an-abilityscore-of-100-200-mean-for-a-child-with-rett-syndrome","title":"What does an AbilityScore of 100–200 mean for a child with Rett Syndrome?","reason":"Same 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gait abnormalities in a young girl.","authority_links":[{"url":"https://icd.who.int","code":"LD90.0","label":"WHO ICD-11 for Mortality and Morbidity Statistics"},{"url":"https://www.who.int","label":"WHO International Classification of Functioning, Disability and Health (ICF)"}],"last_reviewed_at":"2026-06-10T10:52:00.07543+00:00","meta_description":"Rett syndrome is classified under ICD-11-MMS code LD90.0 within developmental anomalies of the nervous system. Definition, coding context and referral guid","related_materials":[],"related_techniques":[]}