Down syndrome

Down syndrome is a chromosomal condition caused by an extra full or partial copy of chromosome 21. It can affect development, learning, speech, hearing, vision, muscle tone, sleep, and multiple organ systems. Health, communication, and support needs vary widely across childhood and adulthood. Use person-first language unless the person expresses another preference.1

Urgent safety

Seek emergency care for blue or gray color, severe breathing difficulty, fainting with poor recovery, a serious injury, or signs of stroke or spinal-cord involvement. New neck pain or abnormal head position with weakness, gait change, loss of hand function, or new bladder or bowel dysfunction needs urgent assessment, especially after trauma.1

Seek prompt clinical review for choking, recurrent respiratory symptoms, marked daytime sleepiness or breathing pauses during sleep, unexplained bruising or pallor, or a significant loss of skills or participation. Do not attribute a new medical, behavioral, or functional change to Down syndrome or aging without assessment.

Diagnosis and genetic mechanism

The extra chromosome 21 material may result from:

• nonmosaic trisomy 21 caused by meiotic nondisjunction;
• mosaic trisomy 21, with more than one cell line;
• a chromosome translocation involving chromosome 21.

The diagnosis is confirmed by chromosome analysis. Prenatal cell-free DNA and other prenatal screens estimate chance; they do not establish the diagnosis. Diagnostic testing and postnatal karyotyping identify the chromosome pattern, which matters for family-specific recurrence counseling. A translocation may be inherited or new, while most other cases are not inherited. Genetic counseling should use the actual chromosome result rather than a single recurrence estimate.1

Health supervision across life

Condition-specific health supervision complements routine primary care. Depending on age and findings, surveillance may include congenital heart disease, hearing, vision, thyroid function, sleep-disordered breathing, feeding and swallowing, growth and nutrition, blood disorders, gastrointestinal and celiac disease, dental health, musculoskeletal concerns, and mental health.1

Screening and treatment schedules differ across childhood and adulthood. They should follow current age-specific guidance and the person's history rather than a generic checklist. Routine restriction from sports or activity is not justified by Down syndrome alone; symptoms and the demands of the activity guide cervical-spine evaluation.1

In adolescents and adults, new memory, language, mood, sleep, mobility, continence, self-care, or behavior changes require a broad medical and psychosocial assessment. Hearing or vision loss, thyroid disease, sleep apnea, pain, depression, medication effects, major life changes, and other treatable causes can resemble regression or dementia.2

Feeding and communication

Feeding and swallowing assessment should consider coughing, choking, respiratory symptoms, prolonged meals, fatigue, growth, hydration, dentition, hearing, posture, and oral-motor function. Diet texture, pacing, positioning, equipment, and exercises require direct assessment.1

Speech intelligibility and expressive language may not reflect understanding or preferences. Hearing loss, motor planning, muscle tone, memory, attention, anxiety, and communication-partner behavior can all affect performance. Speak directly to the person, allow processing time, offer age-respectful choices, and support participation in healthcare, education, work, relationships, and consent.

AAC can supplement speech at any age. Options may include gesture or sign, visual or written supports, communication books, text, and speech-generating systems. Do not prescribe symbols, touch, switches, or eye gaze from the diagnosis. Assess language, literacy, hearing, vision, motor access, fatigue, and the person's goals in real settings. Model AAC, train partners, include personally meaningful and urgent vocabulary, and keep a low-tech backup.3 For evaluation, trials, funding, and implementation, use the AAC device acquisition guide.

Coding

• Q90.0: Trisomy 21, nonmosaicism (meiotic nondisjunction).
• Q90.1: Trisomy 21, mosaicism (mitotic nondisjunction).
• Q90.2: Trisomy 21, translocation.
• Q90.9: Down syndrome, unspecified.

Use the chromosome result when documented; do not select a mechanism-specific code from appearance or assumptions.4

Sources

1. Bull et al. Health Supervision for Children and Adolescents With Down Syndrome — American Academy of Pediatrics age-specific clinical guidance (2022; PMID 35490285).
2. Tsou et al. Medical Care of Adults With Down Syndrome: A Clinical Guideline — evidence-based adult health, change-in-function, and cervical-spine guidance (2020; PMID 33079159).
3. American Speech-Language-Hearing Association: Augmentative and Alternative Communication — individualized, multimodal AAC assessment without cognitive prerequisites.
4. Centers for Medicare & Medicaid Services: FY2026 ICD-10-CM definitions — Q90.0, Q90.1, Q90.2, and Q90.9 descriptors.

Review boundary

This page cannot diagnose Down syndrome or remotely assess breathing, cardiac, cervical-spine, swallowing, blood, or cognitive concerns. Emergencies require immediate local assessment. Screening, genetic, diet, treatment, mobility, education, and communication decisions require direct review with qualified clinicians and the person's participation.