Last modified on 7 September 2012, at 09:13

Handbook of Genetic Counseling/Down Syndrome - Trisomy 21-1

Down Syndrome - Trisomy 21

IntroductionEdit

  • What have you been told about why you were referred to Genetics?
  • Was a prenatal diagnosis of Down Syndrome made?
  • Were chromosome studies performed?
  • What do you already know about Down Syndrome?
  • What are your main concerns? What would you like to gain from this session?

Intake and Family HistoryEdit

  • Explain that all of their concerns will be addressed later in the session, but that I would like to take a medical history and family history first.
  • The history may help us to explain your concerns better.
  • The questions I ask are all standard questions we ask to everyone and does not necessarily mean that any thing you did during pregnancy is responsible for causing a problem with your child.
  • A pedigree helps us identify any health problems that seem to "run in the family". This may include things that may not be directly related to Down Syndrome.
  • While taking the pedigree ask about any family members who have had miscarriages, birth defects, mental retardation, learning difficulties, or health problems
  • Obtain as much psychosocial history as possible throughout the session and address any other questions near the end when available resources are provided and when psychosocial issues or concerns are ascertained and addressed.

EtiologyEdit

  • Most commonly occurring genetic condition
  • Explain chromosomes and nondisjunction which accounts for 95% of cases
  • Unsure why nondisjunction occurs, but the incidence increases with advanced maternal age
  • However, 80% of babies with Down Syndrome are born to women <35 because more children are born to younger women
  • The remaining cases are due to translocation (3-4%) and mosaicism (1-2%)
  • The extra chromosome or chromosome part is what causes the characteristics of Down Syndrome.
  • Stress that there is nothing that they could or could not have done before or during the pregnancy to prevent this from happening
  • Prevalence highly dependent on maternal age 1/1445 at age 20 and 1/25 at age 45

Physical CharacteristicsEdit

  • Children with Down Syndrome are all unique individuals in personality and appearance.
  • They do however have certain physical characteristics in common with other children with Down Syndrome. These Include:
    • Muscle hypotonia (low muscle tone)
    • Flattened midface due to underdevelopment
    • somewhat depressed nasal bridge and small nose
    • Oblique palpebral fissures (an upward slant to the eyes)
    • Epicanthal folds (small skin folds on the inner corner of the eyes)
    • Dysplastic ear, small, low-set, lopped pinnae
    • Simian crease (60%) A single deep crease across the center of the palm
    • Hyperextensible joints
    • Clinodactyly (Dysplastic middle phalanx) of the fifth finger, fifth finger has one flexion furrow instead of two (single interdigital crease)
    • Brachydactyly (shortened fingers)
    • Excessive space between large and second toe (sandal toe)
    • Small mouth, protruding tongue
    • brushfield spots (white fluffy spots on iris)
  • It is important to note that these children generally look much more like their parents than other Down syndrome patients.

Alternative DiagnosisEdit

  • Down Syndrome is common and distinctive and is not often confused with other syndromes.
  • Confusion most common in "normal neonates with one or more of the common signs or minor anomalies, but absence of other common signs and the facial gestalt should avoid the error."
  • Smith Magenis syndrome has some overlapping features including:
    • brachycephaly, round face, upslanting palpebral fissures, midface hypoplasia, small wide nose, Wolfflin-Kruckmann iris spots that may be confulsed with Brushfield spots
    • other signs of Down Syndrome are absent
  • Zellweger syndrome, a peroxisomal disorder which shares findings including:
    • hypotonia, sarge fontanels, flat occiput and face, anteverted nares, epicanthal folds, Brushfield spots, cataracts, abnormal helices, single palmar crease, cardiac septal defects
    • distinguishing signs include: severe early developmental delay, seizures, a high forehead, shallow orbits, hepatomegaly, joint contractures, confirmed by finding elevated plasma very-long -chain fatty acids

Developmental IssuesEdit

  • Mental retardation
    • occurs in most patients with Down Syndrome. With the advent of early intervention and inclusive educational models, there are more individuals with Down syndrome who test within normal IQ range than was previously seen.
    • usually mild - moderate mean IQ is 45-48 and upper limit about 70 (mental age equivalent for mean is 5.5 years and ranges from 1-9 years) but IQ is poor measure of the spectrum of abilities that may be highly variable.
    • no way to predict the severity, but can get a better idea of the degree of mental retardation around the age of two
  • "Children with Down syndrome learn to sit, walk, talk, play, toilet train and do most other activities - only somewhat later than their peers without Down syndrome."
  • "Early intervention services, which begin shortly after birth, help children with Down syndrome develop to their full potential."
  • Most will continue to require some level of day-to-day supervision throughout life, however every year there are more individuals who live independent lives.
  • Some individuals with Down syndrome are able to drive, and it is becoming more common in several countries.

Life Expectancy and Special Health ConcernsEdit

  • 80% live to age 55 and many live even longer
  • mortality rates remain high during the first 5 years because of congenital heart defects, infection, pneumonia, leukemia
  • Congenital heart disease in approximately 40-50% of patients
    • VSD or ASD are most common types
    • AV canal defects and other heart anomalies are also found
    • (all newborns should be seen by cardiologist for an echocardiogram)
  • Pulmonary hypertension
    • common and can mask a heart defect by making a murmur difficult to hear
  • GI anomalies in 10-15 %
    • Duodenal atresia
    • Tracheoesophageal fistula
    • imperforate anus
    • Hirschsprung disease
    • constipation common during infancy
  • Hearing
    • (have hearing checked at birth via auditory brainstem response test (ABR) and every 6 months until 3 years old via behavioral audiology once developmental age of 7-8 months is reached)
    • Frequent ear infections
    • sinusitis
    • conductive hearing loss
  • Opthalmologic
    • Refer for screening by 6 months of age and yearly or for any of the following if suspected:
    • Congenital cataracts
    • Estropia
    • Glaucoma
    • Strabismus
  • Obstructive sleep apnea of some degree in over 60% due to small oropharynx with relatively large tongue.
    • Manifest by loud snoring, stop breathing, waking up a lot throughout the night
  • Hypothyroidism in 10-15% (should screen at 6 months and yearly)
  • Atlanto-axial instability
    • x-ray findings of cervical spine instability in 10%
    • only 1-2% develop spinal compression
    • (x-ray should be scheduled between 3-5 years of age or as needed for special olympics)
  • Hematologic
    • Increased risk of leukemia (15-20 times greater than general population)
    • Majority of cases occur in first 3 years of life with high cure rate
    • Transient form can be seen in newborn and disappear during first 2 - 3 months of life
  • Alzheimer disease
    • Increased risk of about 25% compared to 6% among general population
    • onset in 40's or 50's
  • Most females are fertile, but have reproduction problems (irregular ovulation, miscarriage, preterm labor, etc.)
  • Almost all males are infertile due to defective spermatogenesis

Recurrence Risk for next pregnancyEdit

  • 1% if nondisjunction or maternal age-adjusted risk if that is greater (this represents an increased risk for patients under age 30 and we're unsure why)
  • recurrence risk for familial 14/21 translocation varies according to which parent is affected by balanced Robertsonian translocation (3-5% males 10-15% females)
  • 100% if parent has 21/21 translocation (rare)
  • no increased risk if child has a de novo translocation

Prenatal DiagnosisEdit

  • Screening tests
    • Triple screen can often indicate an increased risk but not diagnostic (70% ascertainment and 5% false positive)
    • Level II ultrasound can pick up signs seen in Downs syndrome, but not diagnostic about 60-66% of fetuses with Down Syndrome are detected
  • Diagnostic testing
  • chorionic villus sampling usually performed at around 10-12 weeks LMP
  • amniocentesis usually performed 15-20 weeks after LMP

Psychosocial IssuesEdit

  • Get a feel for how well they have adjusted to and accepted the idea of having a child with Down Syndrome. "How are you feeling about having a child with Down Syndrome?"
  • Normalize any feelings of grief that they might be experiencing "Many people feel sad and feel like they have lost something when they find out that something might be wrong with their child."
  • Explain that feelings of guilt and blame can be common too, but stress that nothing they could have done would have caused or prevented this.
  • How have other family members and friends reacted? How much support are your receiving? (perhaps if they have other children see who helps take care of them)
  • Alternative placement could be discussed - explain that adoptive homes are available through Down Syndrome Association (waiting list)

ResourcesEdit

  • Provide with written materials
  • Arrange Individualized Family service Plan (IFSP) children birth to 3 and Individualized educational Plan (IEP) from age 4 until end of formal schooling
  • Early Intervention Programs via County Board of MR/DD probably not available for Kentucky residents (Infant program which involves weekly visits at home by a therapist)
  • Financial assistance (Supplemental Security Income? SSI)
  • Follow up letter

ReferencesEdit

  • Health Care Guidelines for Individuals with Down Syndrome: 1999 Revision
  • Reprinted from Down Syndrome Quarterly, Volume 4, Number 3, September, 1999
  • Management of Genetic Syndromes Chapter 7 'Down Syndrome', 2002 Wiley-Liss Inc. editors Cassidy, S.B. and Allanson, J.E.
  • www.ndss.org - National Down Syndrome Society web site
  • www.dsagc.com -- Down Syndrome Association of Greater Cincinnati web site

NotesEdit

The information in this outline was last updated in 2001.