Down Syndrome

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Down Syndrome
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Objectives

• Be familiar with the genetic basis for Down
  Syndrome
• Know the common physical stigmata of Down
  Syndrome
• Be comfortable caring for children with Down
  Syndrome and what testing and routine care is
  recommended

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Etiology

• Most commonly recognized genetic cause of mental
  retardation prevalence of 9.2 cases per 10,000
  live births
• Diagnosed by Karyotype
• 95 - Trisomy 21
• 2 - Mosaicism (mix of diploid and trisomy 21)
• 3 - Robertsonian translocation (part or all of
  extra chromosome 21 fused with another chromosome)

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Etiology

• 95 percent of occurrences of trisomy 21 result
  from nondisjunction during meiotic division of
  the primary oocyte
• Most trisomy 21 pregnancies prove to be nonviable
• 1/4 of fetuses with trisomy 21 survive to term

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Etiology Risk Assessment

• Maternal Age
• 1/1,300 for a 25-year-old woman
• 1/365 for age 35
• 1/30 for age 45
• At age 35, the second-trimester prevalence of
  trisomy 21 (1/270) approaches the estimated risk
  of fetal loss due to amniocentesis (1/200) This
  became cutoff for screening

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Advanced Maternal Age as Risk Factor
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Etiology Risk Assessment

• 15-18 Weeks Gestation triple test detects 60
  of pregnancies affected by trisomy 21
• False positive rate about 5
• Alpha-fetoprotein (AFP), unconjugated estriol and
  human chorionic gonadotropin (hCG)
• Ultrasound in 1st trimester increases
  sensitivity to close to 80 with no change in
  false positive rate

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Etiology Risk Assessment

• Ultrasound in 2nd trimester findings possible
• Intrauterine growth restrictionMild cerebral
  ventriculomegalyChoroid plexus cystsIncreased
  nuchal fold thicknessCystic hygromasEchogenic
  intracardiac fociCongenital heart
  defectsIncreased intestinal echogenicityDuodenal
  atresia ("double-bubble sign")Renal pelvis
  dilationShortened humerus and femurIncreased
  iliac wing angleIncurving (clinodactyly) and
  hypoplasia of the fifth fingerIncreased space
  between first and second toesTwo-vessel
  umbilical cord

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Etiology Risk Assessment
Diagnostic procedure Gestational age when test is done (weeks) Risk of fetal loss ()
Early amniocentesis 10 to 12 0.5 to 1.5
Early amniocentesis 12 to 15 1.0 to 2.0
2nd-trimester amniocentesis 15 to 20 0.5 to 1.0
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Clinical Findings

• Brachycephaly 63-98
• Oblique palpebral
• fissures 70-98
• 1st 2nd toe gap 44-97
• Loose skin on neck 17-94
• Hyperflexibility 47- 92
• Ear abnormalities
• (low folded, stenotic) 28-91
• Protruding tongue and
• small, narrow palate 32-89
• Flat nasal bridge 57-87
• Muscular hypotonia 21-85
• Epicanthal folds 28-79
• Brushfield spots (ring
• of iris speckles) 35-78

• Short fifth finger 51-77
• In-curved fifth finger 43-77
• Short broad hands 38-75
• High arched palate 59-74
• Single palmar crease 42-64
• Cardiac defect
• (1/2 AV canal defects) 40-50
• Transient myelodysplasia
• of the newborn 10
• Duodenal atresia 5-8
• Yellow - Highly specific to Down Syndrome

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Medical Problems By System
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Cardiac

• ALL newborns with the syndrome should have an
  electrocardiogram and a screening echocardiogram,
  even if a murmur is not present.
• Most common anomalies are
• complete atrioventricular canal defects (60
  percent)
• ventricular septal defects (32 percent)
• tetralogy of Fallot (6 percent)
• ostium secundum atrial septal defect (1 percent)
• The long-term prognosis is best when an infant
  with a cardiac defect is promptly referred to a
  pediatric cardiologist for medical management to
  prevent pulmonary hypertension or to a pediatric
  cardiac surgeon for early surgical repair

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Gastrointestinal

• Various defects are associated with Down
  syndrome Esophageal atresia, Tracheoesophageal
  fistula, Pyloric stenosis, Duodenal atresia,
  Meckel's diverticulum, Hirschsprung's disease,
  Imperforate anus
• GERD may require medication
• Constipation usually dietary management is
  enough

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Ear, Nose and Throat Problems

• Midfacial malformations prevent optimal drainage
  of eustachian tubes and sinuses
• susceptible to otitis media, sinusitis and
  pharyngitis
• sequelae can include hearing loss, chronic
  infection, pneumonia, sepsis, endocarditis or
  congestive heart failure in infants with
  concomitant heart defects
• Auditory brainstem response testing to evaluate
  for hearing loss should be performed when an
  infant with Down syndrome by 6 months old

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Orthopedic Problems

• Associated problems Atlanto-occipital
  instability, Atlantoaxial instability,
  Hyperflexibility, Scoliosis, Late hip dislocation
  (after two years of age), Slipped capital femoral
  epiphysis, Patellar subluxation or dislocation,
  Foot deformities
• Xrays of the flexed and extended cervical spine
  were recommended as screening tests in the past
  for atlantoaxial instability when children with
  Down syndrome reach the age of two years or
  before they undergo general anesthesia
• Although screening radiographs are controversial,
  13 of children with Down syndrome have
  asymptomatic atlantoaxial instability that should
  be monitored and that precludes their
  participation in contact sports
• ALL children with Down Syndrome should be
  referred to Early Intervention from birth for
  physical therapy services

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Endocrine Disorders

• Thyroid Disease thyroid function tests should
  be done at birth and at least annually
• Gonadal dysfunction and growth hormone deficiency
  - These problems may require hormonal therapy

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Ophthalmology

• Congenital cataracts - occurs more frequently in
  children with Down syndrome than in other
  children
• Red (fundus) reflexes should be checked at birth.
• Consultation with a pediatric ophthalmologist
  during the first year is necessary
• Ocular problems that may be correctable
  Congenital and acquired cataracts, Nystagmus,
  Strabismus, Dacryostenosis, Blepharitis,
  Keratoconus, Refractive errors (myopia,
  astigmatism), Amblyopia, Increased retinal
  vasculature, Glaucoma

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Other Systems

• Transient myeloproliferative disorder (leukemoid
  reaction) occurs in 10
• Learning point normal infants who exhibit
  leukemoid reactions within the 1st two months of
  life should be evaluated by karyotype for mosaic
  Down syndrome
• Seizures - 5-10 of Down Syndrome children
• Dental Delayed eruption, Atypical patterns of
  eruption, Congenitally missing teeth, Unusually
  shaped teeth, Enamel defects, Orthodontic
  problems, Bruxism, Periodontal disease

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Psychosocial Issues

• Initial Counseling
• If not sure of the diagnosis when initial testing
  done, say so. We are concerned that your child
  shows some signs of Down Syndrome and with your
  permission I would like to draw blood and test
  for this. You should point out what physical
  traits you see to help with denial by the
  parents.
• Try to have both parents present when you talk to
  them - The parents may react with shock, denial,
  anger, grief, fear, acceptance or any combination
  of these emotions. The physician should
  acknowledge the parents' feelings and their right
  to have them
• The infant should be referred to by name, so that
  his or her worth as a human being can be stressed.

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Psychosocial Issues

• The mother and father may benefit from an
  opportunity to meet with the parents of an older
  child with Down syndrome. Such a meeting may
  provide tangible proof that a child with Down
  syndrome can thrive and become a vital part of
  the family
• Provide web based and written resources

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Final Note

• Life tables published in 1989 showed that more
  than 50 percent of infants with Down syndrome
  could be expected to live more than 50 years
• As mortality rates for the operative repair of
  congenital heart defects continue to decrease,
  survival may increase considerably

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Resources

• Books
• Libby Kumin. Communication skills in children
  with Down syndrome a guide for parents.
  Rockville, Md. Woodbine House, 1994.
• Siegfried M. Pueschel. A parent's guide to
  Down syndrome toward a brighter future.
  Baltimore Paul H. Brookes, 1990.
• Kay Stray-Gundersen, ed. Babies with Down
  syndrome a new parents' guide. 2d ed. Bethesda,
  Md. Woodbine House, 1995.
•  
• World Wide Web
• America Online
• --Personal Empowerment Network chatroom (keyword
  PEN)
• --Better Health and Medical Network, disabilities
  forum, support chats, Down syndrome
• Down Syndrome newsgroup http//www.downsyndrom
  e.com (other resources linked to this Web page)  
  
• Organizations
• National Down Syndrome Congress
  1-800-232-6372
• National Down Syndrome Society 1-800-221-4602
  
• National Parent to Parent Support and
  Information System 1-800-651-1151
• La Leche League International (breast-feeding
  information and support) 1-800-525-3243