Ch. 14 Genetic and Developmental Disorders Updated Feb

Chapter 14: Genetic and Developmental Disorders

• Instructor: Mrs. Giomara McBee, PTA, MS, BS, Keiser University

Objectives

• Review major pathologies associated with genetic and developmental conditions.

• Consider anatomic and physiologic aspects affecting treatment choices for individuals with these conditions.

• Theorize treatment interventions based on the goals for each discussed genetic and developmental condition.

Down Syndrome (p. 458)

• Definition: First genetic disorder attributed to chromosomal deviation (Trisomy 21).

• Prevalence: Most common inherited chromosomal disorder; incidence increases with maternal age.

Etiology, Factors, and Pathogenesis (p. 459)

• Down syndrome results from three copies of chromosome 21 due to faulty meiosis.

• Karyotype: 47 chromosomes instead of the normal 46.

Clinical Manifestations (p. 459)

• Physical Features:

  • Flattened nasal bridge (90%)

  • Congenital heart defects

  • Flat occiput; bradycephaly

  • Short limbs

  • Simian line

• Developmental Delays:

  • Language delays

  • Muscle hypotonia

  • Delayed gross motor skills

  • Sensory impairment

  • C-spine atlantoaxial instability

Medical Management (p. 460)

• Screening: Maternal serum screening can detect 60-70% of fetuses with Down syndrome in the second trimester.

• Postnatal Diagnosis: Begins with suspected physical findings.

• Treatment Goals: No cure; focus on helping children reach their full potential.

Prognosis (p. 460)

• Life Expectancy: Improved with medical care, yet remains lower than the general population.

• Historical Context: Average age of death increased from 2 years in 1968 to 55 years in 1997.

Autism Spectrum Disorder (ASD) (p. 460)

• Definition: A group of complex brain development disorders characterized by difficulties with social interaction, communication, and repetitive behaviors.

• Etiology: Not fully understood; thought to be multifactorial (genetic and environmental influences).

Neuropathology of ASD

• Behavioral Symptoms:

  • Sensory seeking or avoidance

  • Attention deficits

  • Difficulty with social cues

  • Verbal challenges

  • Echolalia (repetition of words)

  • Developmental motor delays

• Diagnosis: Autism Diagnostic Observation Schedule is considered the gold standard.

Signs and Symptoms (ASD)

• Onset: Initial signs can appear between two to three years; some may be detected as early as 4-5 months.

• Exceptional Talents: Many children excel in music, art, and academics.

• Classification Levels:

  • Level 1: Mild challenges; requires support.

  • Level 2: Significant challenges; requires substantial support.

  • Level 3: Severe challenges; requires extensive support.

Scoliosis (p. 461)

• Definition: Abnormal lateral curvature of the spine associated with vertebral rotation and rib cage deformity.

• Incidence: Age of onset varies.

• Pathogenesis: Unclear.

Etiological Factors

• Types:

  • Functional Scoliosis: May resolve when underlying cause (e.g., pain, posture) is treated.

  • Structural Scoliosis: Fixed curvature with vertebral rotation.

Clinical Manifestations (p. 461)

• Curvature Degree:

  • Mild: < 20 degrees

  • Severe: > 60 degrees (can lead to pulmonary insufficiency, pain, etc.)

• Postural Changes: Asymmetric shoulder, head, and pelvic alignment.

• Rib Hump: Notable during forward bending (Adam's position).

Medical Management

• Prevention and Early Detection: Key to successful management.

• Conservative Treatments: Aim to improve strength and flexibility; spinal orthoses may stabilize curvature.

• Bracing Options: Milwaukee and Boston braces used based on specific curvature characteristics.

Congenital Neural Tube Defects (NTDs) (p. 465)

• Definition: Includes spina bifida; results from failure of neural tube closure affecting the spinal cord.

Incidence and Etiologic Factors

• Varies among ethnic groups and is linked to genetic and folic acid deficiency.

• Folic Acid: Essential B vitamin for prevention; needs to be taken preconception.

Clinical Manifestations (p. 466)

• Symptoms may include muscle paralysis, LMN presentation, and hip deformities.

• Potential complications: hydrocephalus, bowel/bladder incontinence, clubfoot.

Level of Lesion Outcomes

• Thoracic Lesion: Weak trunk muscles.

• L1-L2: Weak hip flexors; risk of hip dislocation.

• L3-L4: Variability in function and motor capabilities.

Prognosis

• Poor prognosis with total paralysis; overall survival rate to adulthood is 85%.

• Continuous therapy needed to maintain function.

Implications for PTA

• Strategies for managing patients with hydrocephalus and neural tube defects, including proper positioning, muscle assessments, and emphasizing weight-bearing activities.

Muscular Dystrophies (p. 472-473)

• Definition: Largest group of inherited disorders characterized by progressive muscle wasting.

• Primarily affects males; females are carriers.

Duchenne’s and Becker’s Muscular Dystrophy (p. 473)

• Mechanism: Absence of dystrophin leading to muscle cell destruction and replacement with fat/connective tissue.

• Confirmed with DNA analysis and high serum creatine kinase.

Clinical Manifestations (p. 476)

• Characterized by Gower’s sign, progressive weakness, gastrointestinal irregularities, and respiratory weakness.

Medical Management

• Focus: Maintaining muscle function and managing contractures; no cure.

Torticollis (p. 482)

• Definition: Twisted neck due to contracted sternocleidomastoid muscle.

• Etiology: Often related to birth trauma.

Erb’s Palsy (p. 484)

• Definition: Paralysis from traction injury to the brachial plexus during birth.

• Manifestations: Commonly associated with the 'waiter's tip' position.

Osteogenesis Imperfecta (p. 487)

• Definition: Congenital disorder of collagen affecting bone strength.

• Symptoms: Frequent fractures, easy bruising, delayed motor skills.

Medical Management

• Diagnosis involves clinical signs and skin analysis.

• Treatment: Bisphosphonates to improve bone density; fracture prevention strategies emphasized.

Implications for PTA

• Emphasis on careful handling to prevent fractures; engage families on proper care techniques.

Arthrogryposis Multiplex Congenita (p. 491)

• Definition: Non-progressive condition marked by joint contractures from fetal movement reduction.

• Clinical Features: Muscle weakness and joint deformities.

Medical Management (p. 492)

• Strategies: Passive mobilization, strengthening, splinting, and potential surgical interventions.

References

• Goodman C., Fuller K., & Marshall, C. (2017) Pathology for physical therapist assistant. (2nd ed.). St. Louis, MO: Saunders. ISBN: 978032395496

• Kessler, M. (2021). Neurologic interventions for physical therapy (4th ed.). Elsevier.