Genetic Conditions & Pediatric Respiratory Overview

Down Syndrome

• Definition & Epidemiology

  • Genetic condition characterized by an extra copy of chromosome 21 in every somatic cell.

  • Most common chromosomal anomaly diagnosed in the United States.

  • Leading global cause of intellectual disability.

• Cytogenetic Variants

  • Trisomy 21 (Standard)

  • Each cell has three complete copies of chromosome 21.

  • Accounts for ext{≈}95\% of cases.

  • Translocation Down Syndrome

  • A segment of chromosome 21 is attached (translocated) to another chromosome (often 14 or 22).

  • Represents 3\% of diagnoses.

  • Mosaic Down Syndrome

  • Mixture of two cell lines: some cells have the typical two copies of chromosome 21, others have three.

  • Produces milder phenotype in ≈2\% of individuals.

• Risk Factors & Screening

  • Incidence increases with advanced maternal age (≥35 yrs).

  • Routine prenatal screening for all pregnancies:

  • First & second-trimester maternal serum markers.

  • Fetal ultrasound for nuchal translucency & structural anomalies.

  • If screen is positive → diagnostic testing:

  • Chorionic villus sampling (CVS) at 10\text{–}14 wks gestation.

  • Amniocentesis ≥15 wks gestation.

  • Percutaneous umbilical blood sampling (PUBS) in selected scenarios.

• Characteristic Physical Findings

  • Flattened nasal bridge, up-slanting almond-shaped palpebral fissures.

  • Single transverse palmar (simian) crease.

  • Short neck with excess skin folds.

  • Small pinnae; protruding tongue relative to oral cavity.

• Common Comorbidities

  • Congenital heart defects (e.g., AV canal).

  • Obstructive sleep apnea.

  • Ophthalmologic & hearing disorders.

  • Gastrointestinal anomalies (duodenal atresia, Hirschsprung disease).

  • Hematologic: iron-deficiency anemia, leukemia (esp. ALL & AML-M7).

  • Endocrine: hypothyroidism.

• Development & Learning

  • Mild–moderate intellectual disability; global developmental delays.

  • Sensory-processing challenges → delayed milestones.

  • Speech often delayed; non-verbal communication preferred early.

• Nursing & Interdisciplinary Management

  • Early intervention within first month of life (PT, OT, ST).

  • Break ADLs into smaller steps; emphasize strengths.

  • Annual screening of:

  • Medical issues, nutrition, accident risk.

  • Financial & psychosocial needs of family.

  • School-age: IEPs, classroom aide to enhance social integration; include siblings in care plans.

  • Genetic counseling offered to all families (recurrence risk ≈1\% for trisomy; higher for translocation carriers).

Fragile X Syndrome

• Etiology & Genetics

  • Caused by mutation (CGG trinucleotide repeat expansion) of the fragile‐X messenger ribonucleoprotein gene (FMR1) on the X chromosome.

  • Most common inherited form of developmental/intellectual disability.

• Inheritance Pattern

  • X-linked dominant with variable penetrance.

  • Females (carriers): 50\% chance of transmitting mutation to each child.

  • Males (full mutation): transmit mutated X to all daughters (obligate carriers), none to sons.

  • Genetic counseling recommended for suspected cases & carrier families.

• Physical Manifestations (become prominent peri-/post-puberty)

  • Long, narrow face with prominent forehead & chin.

  • Large, protruding ears; macrocephaly.

  • Joint laxity; pes planus (flat feet).

  • Macro-orchidism (enlarged testes) in post-pubertal males.

• Cognitive & Behavioral Features

  • Early childhood: language delays, sensory-processing disorders.

  • Social anxiety, shyness, poor eye contact.

  • Learning deficits ranging from mild difficulties to severe disability; females usually milder.

• Common Comorbidities

  • Recurrent otitis media & sinusitis.

  • Visual refractive errors.

  • Mitral valve prolapse.

  • Seizure disorders.

• Management

  • Individualized, multidisciplinary: speech, occupational, behavioral therapies.

  • School-based supports (IEP, assistive communication devices).

  • Ongoing monitoring for ENT issues, cardiac function, seizures.

Pediatric Respiratory Review

Anatomy Differences (Child vs. Adult)

• Obligate nose breathing from birth until \approx 6 months → nasal swelling can rapidly compromise airway.

• Chest wall nearly circular; weak intercostals → rapid fatigue.

• Oral cavity: larger tongue, base directly contacts epiglottis.

• Narrow nasal passages; short pharynx, enlarged adenoids/tonsils.

• Larynx positioned anteriorly; epiglottis higher & more horizontal.

• Trachea: shorter, narrower, less cartilaginous support.

• Alveolar count: \approx 17\text{ million} at birth vs 600\text{ million} in adults.

• Fewer developed paranasal sinuses; proportionally larger head & shorter neck.

Adventitious Breath Sounds

• Wheezing: high-pitched musical sound (mostly on expiration) → obstruction, asthma, viral bronchiolitis.

• Rales (Crackles): popping sounds from fluid-filled alveoli (e.g., pneumonia, pulmonary edema).

Acute Respiratory Infections (ARIs)

• Transmission: direct contact & respiratory droplets.

• Pathophysiology: viral invasion → airway inflammation, mucosal edema, ↑ secretions.

• Incubation: 1\text{–}3 days; symptomatic phase 4\text{–}10 days.

• Upper Respiratory Infections (URIs)

  • Most frequent ARI category; highest incidence in children <5 yrs.

  • Predominantly viral; peak in winter/spring.

  • Pediatric anatomy predisposes to more severe manifestations.

Risk Factors & Epidemiology

• Immature immune system → limited adaptive responses.

• High exposure (daycare, school) & behavioral hand-to-mouth tendencies.

• Viral shedding higher & longer vs adults → easier spread.

Clinical Assessment

• Observe rate, rhythm, effort; note retractions, nasal flaring, head bobbing.

• Auscultate lungs for adventitious sounds.

• Skin: color (pallor, cyanosis), temperature, moisture.

• History: onset/duration, exposures, prior treatments, birth & prenatal details.

Symptom Spectrum

• Mild: sneezing, cough, conjunctival drainage, fatigue, headache, low-grade fever.

• Severe/Distress Indicators:

  • Tachypnea; increased WOB (retractions, grunting).

  • Unexpected lung sounds (wheezes, crackles).

  • Hypoxia (± hypercapnia): altered mental status.

Diagnostics

• Mild cases: clinical diagnosis; no labs.

• Point-of-care tests: throat culture, rapid influenza A/B, RSV, COVID-19 swabs.

• Imaging: chest X-ray if pneumonia or severe distress suspected.

• CBC, blood gas for hospitalized or worsening patients.

Management Principles

• Primarily supportive for viral URIs: hydration, antipyretics, nasal saline/suction.

• Escalation for bacterial superinfection (e.g., antibiotics for streptococcal pharyngitis).

• Hospitalization criteria: persistent hypoxia, apnea, dehydration, inability to maintain PO intake, worsening distress.

Psychosocial & Developmental Considerations

• Child’s response influenced by developmental stage, prior medical experiences, family support.

• Promote coping: age-appropriate explanations, parental presence, therapeutic play.

Health Promotion & Disease Prevention

• Ensure routine well-child visits and immunizations (e.g., influenza, COVID-19, pneumococcal, pertussis).

• Parent education: hand hygiene, environmental cleaning (toy washing), limiting sick contacts.

• Recognize early signs of distress; seek timely care.