5.3 BNU2363 Paediatric Nursing: Caring for Special Needs: Down Syndrome (DS)

Definition and Chromosomal Basis of Down Syndrome (DS)

• General Definition: Down Syndrome is a condition in which a person has an extra chromosome, classified as a chromosomal anomaly.

• Chromosomal Count: Individuals with Down Syndrome typically have a total of $47$ chromosomes instead of the usual count of $46$.

• Specific Abnormality: The condition involves an extra copy of chromosome $21$, often referred to as Trisomy $21$.

• Impact: This genetic variation causes fundamental changes in the way the body and brain develop.

Etiological Classification: Types of Trisomy 21

There are three primary ways Down Syndrome occurs, categorized by the nature of the chromosomal division or attachment:

• Complete Trisomy 21

  • Mechanism: During meiosis, chromosomes line up to divide and create eggs or sperm. In this type, non-disjunction occurs. This means an egg is gifted with two $21^{st}$ chromosomes rather than the standard one.

  • Fertilization Impact: Once the egg is fertilized, the resulting zygote has a total of three copies of chromosome $21$.

  • Prevalence: This is the most common cause of Down Syndrome.

• Translocation Trisomy 21

  • Mechanism: There are two copies of chromosome $21$, but extra material from a third $21^{st}$ chromosome is attached (translocated) to another chromosome.

  • Timing and Heredity: This can occur either before or after conception. This is the only form of Down Syndrome that may sometimes be passed down or inherited from a carrier parent.

• Mosaic Trisomy 21

  • Mechanism: This occurs after conception for reasons that remain unknown. Unlike the other types, only some cells in the body have an extra copy of chromosome $21$, while others maintain the normal chromosomal count.

  • Prevalence: This is the least common form of Down Syndrome.

  • Clinical Presentation: The characteristics are less predictable than complete or translocation types. Symptoms may be less obvious depending on the specific location and number of cells that contain the third chromosome $21$.

Epidemiological Risk Factors and Incidence

• Advancing Maternal Age: The risk of a woman giving birth to a child with Down Syndrome increases with age. This is attributed to the fact that older eggs have a significantly greater risk of improper chromosome division.

• Carrier Status: Individuals who are carriers of the genetic translocation for Down Syndrome are at higher risk of passing it to offspring.

• Previous History: Parents who have already had one child with Down Syndrome are at an increased risk for subsequent pregnancies.

Incidence Risk by Maternal Age

• Age 25: $1 \text{ in } 1,250$

• Age 30: $1 \text{ in } 900$

• Age 35: $1 \text{ in } 350$

• Age 40: $1 \text{ in } 100$

• Age 45: $1 \text{ in } 30$

• Age 49: $1 \text{ in } 10$

Longitudinal Longevity Trends

According to data from the Centers for Disease Control and Prevention and the Seattle Times, people with Down Syndrome are living significantly longer:

• 1980s: Average life expectancy was approximately $25$ years.

• 1990s: Average life expectancy rose to approximately $50$ years.

• Today: Average life expectancy has reached approximately $56$ years (with some sources indicating a range up to $60$ years).

Clinical Manifestations and Morphological Features

General Physical Findings

• Decreased muscle tone (hypotonia) at birth.

• Excess skin located at the nape of the neck.

• Separated joints between the bones of the skull (sutures).

• A single palmar crease (Simian crease) in the palm of the hand.

• Wide, short hands with short fingers.

Key Facial and Ocular Characteristics

• Eyes:

  • Upward slanting palpebral fissures (upward slanting eyes).

  • Epicanthal folds: An upper eyelid skin fold that covers the inner corner of the eye.

  • Bushfield spots (also termed Brushfield spots): Small, typically white spots arranged in a ring on the colored part of the eye (the iris).

• Nose: Flattened nasal bridge and flattened nose.

• Ears: Low-set, small, and folded ears.

• Mouth: Typically small mouth.

• Neck: Generally characterized as a short neck.

Medical and Developmental Co-morbidities

Physical Medical Conditions

• Congenital Heart Defects: Specifically atrial septal defect and ventricular septal defect (ASD/VSD).

• Ocular Problems: Cataracts (often requiring glasses).

• Gastrointestinal (GI) System:

  • GI blockages such as esophageal atresia and duodenal atresia.

  • Chronic constipation.

• Otolaryngology: Regular ear infections and associated hearing problems.

• Musculoskeletal: Hip problems, including an increased risk of dislocation.

• Endocrine: Underactive thyroid (hypothyroidism).

• Respiratory: Sleep apnea.

• Dental: Teeth often appear later than normal, which can lead to problems with chewing.

Mental and Social Development

• Impulsive behavior.

• Poor judgment.

• Short attention span.

• Slow learning pace.

Screening and Diagnostic Procedures

Screening Tests (Identification of Risk)

• Blood Tests: Maternal serum alpha-fetoprotein (MS-AFP).

• Ultrasound: Used to detect extra fluid behind the baby's neck (nuchal translucency).

Diagnostic Tests (Confirmation via Chromosomal Analysis)

• Chorionic Villus Sampling (CVS): Examines material directly from the placenta.

• Amniocentesis: Examines the amniotic fluid from the sac surrounding the baby.

• Percutaneous Umbilical Blood Sampling (PUBS): Examines blood drawn from the umbilical cord.

Multidisciplinary Management and Therapeutic Interventions

Developmental and Mental Health Support

• Behavioral training.

• Teaching families methods to deal with frustration, anger, and compulsive behaviors in the child.

• Special education and specialized training.

• Speech therapy.

• Occupational therapy.

• Mental health support.

• Support Groups:

  • National Down Syndrome Society: $www.ndss.org$

  • National Down Syndrome Congress: $www.ndsccenter.org$

Medical and Surgical Management

• Surgery: Immediate surgery may be required after birth for gastrointestinal blockages or to repair congenital heart defects.

• Nutritional Support: Breastfeeding support is recommended.

• Obesity Management: Encouraging plenty of physical activity and avoiding high-calorie foods to prevent obesity.

• Prophylaxis: Use of antibiotics to prevent heart infections like endocarditis.

Nursing Diagnoses in Down Syndrome

• Delayed Growth and Development: Related to chromosomal abnormality and cognitive impairment; evidenced by slow learning and short attention span.

• Impaired Physical Mobility: Related to decreased muscle tone; evidenced by poor muscle strength.

• Impaired Verbal Communication: Related to delayed cognitive and speech development; evidenced by difficulty expressing needs and delayed speech abilities.

• Activity Intolerance: Related to decreased muscle strength and congenital heart defects; evidenced by fatigue, weakness, and inability to tolerate physical activity.

Systematic Healthcare Monitoring Timeline

Birth to 6 Weeks

• Thyroid: Newborn routine heel prick (blood spot test).

• Eye Checks: Newborn routine check, including screening for congenital cataracts.

• Hearing: Universal newborn hearing screen.

• Growth: Length, weight, and head circumference plotted frequently on Down Syndrome-specific growth charts.

• Heart: Formal assessment including Echocardiogram by age $6$ weeks.

• Blood: Newborn blood test to check for abnormal blood film.

Preschool Stage (Under 2 Years to Age 4)

• Thyroid: From age $1$ year, thyroid function discussed annually using an annual fingerprick TSH test OR $2$-yearly thyroid blood tests including antibodies.

• Vision (Age 18–24 months): Formal examination for squint and refraction (long or short sight).

• Vision (Age 4 years): Formal examination for squint, refraction, and assessment of near/distant vision and visual acuity. Monitoring visual behavior at every review.

• Hearing: Full audiological review by $10$ months (hearing test and impedance check); followed by annual audiological reviews.

• Growth: Annual height and weight plotting on DS-specific charts.

• Breathing: Enquire at every review for uneven breathing during sleep or poor quality sleep; low threshold for sleep studies.

• Blood: If blood film was abnormal in first $6$ weeks, follow-up or repeat testing until age $5$.

School Age and Adolescence

• Vision: Repeat tests every $2$ years or more frequently if recommended.

• Hearing: $2$-yearly audiological reviews.

• Growth: Annual monitoring of height, weight, and BMI if overweight is a concern.

• Heart: Low threshold for heart status review if symptoms develop; from adolescence onwards, listen for signs of acquired heart disease during routine checks.