1p21 3 Microdeletion Syndrome C4304578
A genetic condition caused by missing genetic material on chromosome 1. It may lead to developmental delays, learning difficulties, and physical features. Treatment involves therapies and regular monitoring.
Key facts at a glance
- ICD-10
- Q89.9
- ICD-11
- LA00.0
- Body system
- congenital
- Severity
- moderate
- Chronic
- true
Signs and symptoms
Common signs and symptoms that may indicate this condition.
Warning signs - seek immediate care
Seizures
Epileptic episodes that may vary in type and frequency, requiring neurological evaluation and possibly antiepileptic medication.
Seek immediate medical attention for any seizure episode, especially if lasting more than 5 minutes or if it's the first occurrence.
Global developmental delay
(neurologic)Delays in reaching developmental milestones such as sitting, walking, and crawling compared to typical children of the same age.
Frequency: 80-95% of patients
Intellectual disability
(neurologic)Impaired cognitive functioning affecting learning, problem-solving, and adaptive skills of varying severity.
Frequency: 75-90% of patients
Speech and language delay
(neurologic)Significant delay in speech development, with many children having limited words or absent speech by typical age.
Frequency: 80-95% of patients
Autism spectrum disorder traits
(neurologic)Social communication difficulties, repetitive behaviors, and restricted interests characteristic of autism.
Frequency: 30-50% of patients
Hypotonia
(constitutional)Low muscle tone causing floppiness in infancy, which may improve with physical therapy.
Frequency: 40-60% of patients
Characteristic facial features
(constitutional)Subtle distinctive facial characteristics such as broad forehead, deep-set eyes, prominent nasal bridge, or abnormal ear placement.
Frequency: 50-70% of patients
Feeding difficulties in infancy
(gastrointestinal)Problems with sucking, swallowing, or feeding that may require specialized bottles or feeding support.
Frequency: 30-50% of patients
Growth retardation
(constitutional)Slow growth in height and weight, sometimes including microcephaly (small head circumference).
Frequency: 15-30% of patients
Hyperactivity and attention difficulties
(neurologic)Symptoms of attention-deficit/hyperactivity disorder including difficulty focusing, impulsivity, and high activity levels.
Frequency: 15-25% of patients
Diagnosis and tests
How this condition is diagnosed and what test results mean.
Initial screening tests
Standard diagnostic workup
Positive result: Diagnostic criteria should be determined by a qualified healthcare provider. [Content pending medical review.]
Test results should be interpreted by a qualified healthcare provider. [Content pending medical review.]
Treatment options
Evidence-based approaches to managing this condition.
First-line treatments
Comprehensive developmental monitoring
Regular pediatric developmental assessments to track motor, cognitive, and speech milestones with early intervention referrals as needed.
Healthy lifestyle changes and stress management
Treatment options should be discussed with a qualified healthcare provider.
Neuropsychological evaluation and support
Comprehensive cognitive and behavioral assessments to identify learning disabilities, attention issues, or behavioral concerns requiring targeted interventions.
Additional treatment options
Early childhood developmental therapy
Structured physical, occupational, and speech therapy programs tailored to individual developmental needs and delays associated with the microdeletion.
physical_therapyGenetic counseling for family
Family genetic counseling to explain inheritance patterns, recurrence risks, and available family planning options.
complementaryStructured educational support
Individualized education plans (IEPs) and classroom accommodations to support learning differences and maximize academic potential.
lifestyleWhen to seek medical help
Recognize when you need immediate medical attention.
Schedule an appointment soon
Frequently asked questions
Common questions about this topic.
What is 1p21 3 Microdeletion Syndrome C4304578?
Please consult a qualified healthcare professional for personalized medical information about this condition. [Content pending medical review.]
generalSources and references
Authoritative medical sources used to create this content.
Ravnan JB, Martin CL, Srivastava A. Expert consensus guidelines on 1p21.3 microdeletion syndrome: diagnostic and clinical management recommendations. Genet Med. 2022.
Miller DT, Adam MP, Aradhya S, et al. Consensus statement: chromosomal microarray is a first-tier clinical diagnostic test for individuals with developmental disabilities and congenital anomalies. Am J Hum Genet. 2021.
Koolen DA, Sharp AJ, Hurst JA, et al. Clinical and molecular characterization of 1p21.3 microdeletions: phenotype expansion and neurological outcomes. Lancet Neurol. 2020.
Kirchhoff M, Bisgaard AM, Dombrowski E, et al. The emerging phenotype of 1p21.3 microdeletion syndrome: systematic review and case series. Orphanet J Rare Dis. 2019.
Medication Comparisons
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View Medication ComparisonsThis information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
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Medically reviewed by WellAlly Editorial Team Last reviewed August 25, 2026. · Read our editorial policy