pediatrics
Down Syndrome (Trisomy 21)
Diagnosis of Down Syndrome
Prenatal chorionic villus sampling and/or amniocentesis with karyotyping Postnatal karyotyping (if prenatal karyotyping not done) (See also Genetic Diagnostic Technologies .) Diagnosis of Down syndrome may be suspected prenatally based on Physical anomalies detected by fetal ultrasonography Maternal serum screening Noninvasive prenatal screening (NIPS) Fetal ultrasonographic anomalies include increased nuchal translucency, atrioventricular canal defect, and duodenal atresia, but these are not present in all fetuses with trisomy 21. Maternal serum testing may show abnormal levels of plasma protein A in late first trimester and alpha-fetoprotein, beta-hCG (human chorionic gonadotropin), unconjugated estriol, and inhibin in early second trimester (15 to 16 weeks gestation). More recently, Screening (NIPS), in which fetal DNA obtained from the maternal circulation is tested, has become a screening option for trisomy 21 because it has good sensitivity and specificity. If Down syndrome is suspected based on maternal serum screening tests or ultrasonography, fetal or postnatal confirmatory testing is recommended. Fetal confirmatory methods include Chorionic Villus Sampling and/or In high-resource settings, maternal serum screening and diagnostic testing for Down syndrome are usually available to all women who present for prenatal care before 20 weeks gestation regardless of maternal age. The American College of Obstetricians and Gynecologists Committee on Practice Bulletins–Obstetrics, Committee of Genetics, and the Society for Maternal–Fetal Medicine2020 practice bulletin regarding screening for chromosomal abnormalitiesadvises that cell-free fetal DNA analysis be offered to all pregnant women regardless of age or additional risk factors. If diagnosis is not made prenatally, then neonatal diagnosis is based on physical anomalies and confirmed by cytogenetic testing, preferably karyotyping. Certain age-specific routine screening of affected infants and children helps identify conditions associated with Down syndrome ( Diagnosis references ): Echocardiography: At prenatal visit or at birth Thyroid screening (thyroid-stimulating hormone [TSH] levels): At birth, 6 months, 12 months, and annually thereafter Complete blood count (CBC) with differential and either a combination of ferritin and C-reactive protein (CRP) or a combination of serum iron and total iron-binding capacity (TIBC): At 1 year and annually thereafter Hearing evaluations: At birth, every 6 months thereafter until normal hearing established (about age 4 years), then annually (more frequently if indicated) Ophthalmology evaluation: By 6 months, then annually until age 5; then every 2 years until age 13 and every 3 years until age 21 (more frequently if indicated) Growth: Height, weight, and head circumference plotted at each health supervision visit using a Down syndrome growth chart Sleep study for obstructive sleep apnea: Completed by age 4 years Routine screening for atlantoaxial instability and celiac disease is not recommended; children are tested based on clinical suspicion. It is recommended that patients with a history of neck pain, radicular pain, weakness, or any other neurologic symptoms that suggest myelopathy have x-rays of the cervical spine in the neutral position; if no suspicious abnormalities are seen, they should have x-rays done in flexion and extension positions. Medical care guidelines for adults with Down syndrome published by a panel of experts includes recommendations to screen for the following associated diseases (with recommended age to begin screening) ( Diagnosis references ): Diabetes: Hemoglobin A1C or fasting glucose every 2 to 3 years starting at age 30 or at age 21 for those with comorbid obesity Hypothyroidism: Thyroid-stimulating hormone (TSH) every 1 to 2 years starting at age 21 Alzheimer-type dementia: Annual assessment starting at age 40 1.Bull MJ, Trotter T, Santoro SL, et al: Health supervision for children and adolescents with Down syndrome.Pediatrics149(5):e2022057010, 2022. doi: 10.1542/peds.2022-057010 2.Tsou AY, Bulova P, Capone G, et al: Medical Care of Adults With Down Syndrome: A Clinical Guideline.JAMA324(15):1543-1556, 2020. doi: 10.1001/jama.2020.17024 