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Special Pops (Review Q's/Re-outlined PPT) > Genetic Disorders > Flashcards

Genetic Disorders Flashcards

1
Q

3 causes of disease

A
  • Genetic
    • E.g. Cystic fibrosis, sickle cell disease
  • Purely environmental
    • E.g. mercury poisoning
  • Combination
    • E.g. Diabetes mellitus type II, HTN
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2
Q

3 types of purely genetic disease

A
  • Monogenic: Mendelian inheritance, a single gene is involved
  • Polygenic: complex inheritance pattern, many genes are involved

Cytogenic: involves large scale changes in chromosomes

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3
Q

human somatic cells

A
  • 23 pairs of different chromosomes in nuclei (22 autosomes, 1 pair of sex chromosomes)

Members of each pair of autosomes are homologs (1 derived from mother, 1 from father)

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4
Q

genetics terms

gene, locus, allele, homozygous, heterozygous, genotype, phenotype

A
  • Gene: length of DNA that codes for a specific protein
  • Locus: specific location of a gene on a chromosome
  • Allele: different DNA sequence for a particular gene
  • Homozygous: same alleles
  • Heterozygous: different alleles
  • Genotype: refers to a person’s individual alleles and precise genetic makeup
  • Phenotype: physical or physiological manifestation of genotype
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5
Q

genetics terms:

cytogenics, karyotype, FISH, Array Comparative Genomic Hybridization

A
  • Cytogenics: study of chromosomes and their abnormalities
  • Karyotype: chromosomes are displayed according to their length
    • Usually obtained from the lymphocytes in the blood (46XX, 46XY)
  • FISH: uses chemically tagged chromosome specific DNA probe to label a chromosome and visualize it under a fluorescent microscope
  • Array Comparative Genomic Hybridization: compares the child’s DNA with a control DNA to identify microdeletions or microduplications
    • Revolutionized cytogenetic testing
    • High diagnostic yield of genomic abnormalities
    • This technique is replacing FISH for subtelomere imbalances
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6
Q

4 categories of genetic disorders

A
  1. Chromosomal
  2. Single gene
  3. Multifactorial
  4. Mitochondrial
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7
Q

chromosomal disorders

A
  • Altered structure or number
  • Types
    • Deletions
    • Inversions
    • Duplications
    • Translocations
  • Incidence
    • 10-15% of human conceptions
    • 1/160 live births
  • Leading cause of miscarriage
  • Generally are not hereditary
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8
Q

characteristics of chromosomal disorders

A
  • Most are associated with developmental delay and cognitive impairment
  • Large number of genes are involved with CNS development
  • Characteristic craniofacial features
  • Delayed growth, congenital malformations
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9
Q

characteristics of chromosomal disorders

A
  • Most are associated with developmental delay and cognitive impairment
  • Large number of genes are involved with CNS development
  • Characteristic craniofacial features
  • Delayed growth, congenital malformations
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10
Q

Chromosomal Disorders: Alterations in Number

A
  • Polyploidy: complete extra set (all are lethal)
  • Aneuploidy: absence (monosomy) or duplication (trisomy) of a chromosome in a cell
    • Usually only one chromosome is affected
  • Autosomal monosomy
    • Rarely survive
  • Mosaicism: most are due to a full trisomy conception followed by loss of extra chromosomes in some cells during mitosis in the embryo
    • Milder clinical manifestation
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11
Q

common trisomies

A
  • Down Syndrome (trisomy 21)
  • Edwards Syndrome (trisomy 18)
  • Patau Syndrome (trisomy 13)
  • *Nearly all are associated with advanced maternal age
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12
Q

Chromosomal Disorders: Alterations in Structure

A
  • Deletion: caused by a chromosome break
  • Translocation: interchange of genetic material between nonhomologous chromosomes
  • Reciprocal translocation: two breaks in different chromosomes with an equal exchange of genetic material
    • Carriers are usually normal but not offspring
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13
Q

single gene disorders

A
  • Types
    • Autosomal dominant
      • Osteogenesis imperfecta
      • Tuberous sclerosis
      • Neurofibromatosis
    • Autosomal recessive
      • Cystic fibrosis
      • Hurler Syndrome
      • PKU
      • SMA
    • Sex linked
      • Hemophilia A
      • Fragile X
      • Lesch-Nyhan
      • Rett
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14
Q

Monogenic diseases of enzyme proteins

A
  • Genetic mutations in the genes that code for enzymes are the culprit behind enzyme deficiency
  • Enzyme deficiency leads to accumulation of precursors and likely disease
  • “Metabolic disorders”
    • Amino acid metabolism
    • Carbohydrate metabolism
    • Lysosomal storage
    • Urea cycle disorders
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15
Q

polygenic disease

A
  • For many common diseases, genetic susceptibility genes are implicated as opposed to single gene inheritance
  • Genetic patterns in these disorders are difficult to study because of the many factors involved
  • Traits in which variation is thought to be caused by the combined effects of multiple genes are polygenic traits
  • When environmental factors are also believed to cause variation in that trait, the term multifactorial is used
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16
Q

multifactorial disorders

A
  • Autism: a severe neurodevelopmental disorder in which 15 susceptibility loci have been identified that each make an additive contribution to the phenotype
  • Type 1 Diabetes Mellitus: an autoimmune disorder involving immune destruction of the beta cells
    • Many loci implicated in this disease, with at least 12-20 minor susceptibility loci and one major locus discerned in humans
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17
Q

core competencies for health care professionals

A
  1. Need to know how and when to make a referral
    • *PTs practice as independent and skilled practitioners
    • Need to identify S&S and take appropriate family history
  2. Understand the disease etiology and pathogenesis, prognostic indicators, treatment ramifications, neurological outcomes, and lifespan issues
  3. Appreciate one’s limitations in genetics and expertise and identify the need for continuing education
  4. Understand the psychosocial and ethical implications of genetic service
  5. Know when and how to make a referral
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18
Q

Genetic Diseases: When to Make a Referral

A
  • History of dysmorphology
  • Brain malformations
  • Epilepsy
  • Abnormal CT
  • EEG
  • Abnormal tone
  • Weakness
  • Motor control
  • Discoordination
  • Delayed development
  • Sensory disturbances
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19
Q

psychosocial aspects

A
  • Early genetic testing is important for family planning
  • Preimplantation genetic testing
  • Respect for the family’s decision regardless of the outcome of genetic testing
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20
Q

3 forms of down syndrome

A
  • Trisomy 21
    • Most common form
  • Translocation
    • The extra chromosome 21 is attached to another chromosome (usually 14, 21, or 22)
  • Mosaicism
    • Least frequent form
    • Some cells have 47 chromosomes and some have 46
    • Parents may be a carrier and at increased risk
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21
Q

general phenotypic features of down syndrome

A

Hypoplasia is a common element in many of the phenotypic features of individuals with Down Syndrome

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22
Q

other features of down syndrome

A
  • Craniofacial
  • MSK/epicanthal folds
  • Eyes/vision and ears/hearing
  • Cardiovascular
  • Gastrointestinal
  • Neurological
  • Immunologic
23
Q

Craniofacial features of down syndrome

A
  • Inner epicanthal folds
  • Upward slanting palpebral fissures
  • Flat facial profile
  • Aplasia/hypoplasia of frontal sinuses
  • Anomalous ears
  • Low nasal bridge
  • Shortened palate
  • Maxillary and dental hypoplasia
  • Irregular tooth placement
24
Q

MSK features of down syndrome

A
  • Diastasis recti
  • Hypoplasia of the middle phalanx of the 5th with clinodactyly
  • Joint hypermobility
  • Hypoplastic pelvis with shallow acetabular angle
  • Atlantoaxial instability with risk of SC compression
  • Wide gap between toes 1-2
  • Simian creases
  • Linear growth deficits
    • Greatest between 6-24 months
    • Mostly due to leg length reduction
  • Delayed skeletal maturation rate
  • 1/3 overweight by age 3
25
Q

eyes/vision features of down syndrome

A
  • Iris speckling (Brushfield’s spots)
  • Myopia
  • Nystagmus
  • Strabismus
  • Tear duct blockage
  • Conductive hearing loss
  • Sensorineural or mixed hearing loss
    • As many as 78%
26
Q

Cardiovascular features of down syndrome

A
  • Congenital heart disease is the most common problem
    • 40% have malformations
    • Ventricular septal defect
    • Patent ductus arteriosus
    • Tetralogy of Fallot
27
Q

GI features of down syndrome

A
  • Duodenal stenosis/atresia
  • Imperforate anus
  • Hirschprung’s Disease
28
Q

Neurologic features of down syndrome

A
  • Mild microcephaly
  • Hypotonia
  • Intellectual deficits
  • Developmental delay
  • Early onset of Alzheimer’s Disease
  • Small cerebellum and brainstem
  • Reduced number of neurons and dendritic spines
  • Increased latency of response
  • Delayed dissolution of primitive reflexes
    • Plantar, palmar, moro, automatic stepping
  • Delayed emergence of reactive responses
29
Q

Immunologic features of down syndrome

A
  • Leukemia
  • Chronic rhinitis and conjunctivitis
  • Fluid in the middle ear
30
Q

aging considerations for down syndrome

A
  • Life expectancy has been increasing
  • Current life expectancy is 55 years
    • Compared to 9 years in 1929
  • Changes in body function and structure secondary to aging have the potential to lead to activity restrictions
31
Q

thyroid dysfunction and down syndrome

A
  • Adults are at risk for developing both hyper and hypothyroidism as they age
    • Hypothyroidism more common (40% of pts with DS)
  • Untreated hypothyroidism can mimic cognitive decline (may be misdiagnosed as Alzheimer’s Disease
    • Other S&S
      • Decreased energy
      • Decreased motivation
      • Weight gain
      • Constipation
      • Bradycardia
      • Dry skin
32
Q

cardiovascular disorders and aging with down syndrome

A
  • Cardiovascular disorders
    • Occur with aging
    • Mitral prolapse for 46-57%
    • Can lead to increased risk of
      • Endocarditis
      • CVA
      • Heart failure
    • Can occur even without prior abnormal cardiac findings
    • Early S&S
      • Fatigue
      • Irritability
      • Weight gain
      • Dyspnea with physical activity
      • Bilateral crackles that do not clear with a cough
      • A third heart sound
33
Q

cardiovascular capacity with aging and down syndrome

A
  • Lower cardiovascular capacity than peers who are mentally challenged without DS
  • Lower mean peak oxygen consumption, minute ventilation, and HR during exercise testing
  • Secondary to
    • Lower lean body muscle mass
    • Lower muscle strength
    • Thyroid disorders
    • Hypotonia
    • Higher incidence of obesity
    • Impaired sympathetic response to exercise
34
Q

msk disorders with down syndrome and aging

A
  • Premature aging may lead to early experience of MSK disorders generally associated with elderly populations
    • Mid cervical arthritis
    • Hip dysplasia with dislocation
    • Foot pronation
    • Osteoporosis
35
Q

down syndrome, aging and cog concerns

A
  • Alzheimer’s Disease
    • Almost all adults with DS over age 40 demonstrate neuropathology consistent with AD
      • Caused by an over expression of the gene for amyloid precursor protein 🡪 increased accumulation of beta amyloid
  • Depression
    • Mental illness occurs in approximately 30% of adults with DS
36
Q

other frequent conditions with down syndrome and aging

A
  • Middle ear infections
    • Conductive hearing loss increased with age
  • Increased risk for visual impairment
    • Cataracts
    • Blepharitis
    • Keratoconus
    • Excessive myopia
  • Skin disorders
    • Atopic dermatitis
    • Fungal infections
  • Sleep apnea
37
Q

3 defining characteristics of turner’s syndrome

A
  • Sexual infantilism
  • Congenital webbed neck
  • Cubitus valgus
38
Q

other characteristics of turner’s syndrome

A
  • Dorsal edema of hands/feet
  • Hypertolerorism
  • Epicanthal folds
  • Ptosis of the upper eyelids
  • Elongated ears
  • Shortening of the hand bones
  • Skeletal abnormalities
    • Hip dislocation
    • Pes planus
    • Pes equinovarus
    • Dislocated patella
    • Deformity of medial tibial condyles
    • scoliosis
39
Q

etiology of marfan syndrome

A
  • Gene that codes for fibrillin protein (an elastic protein in CT) is FBN1 located on chromosome 15
  • Mutation of this gene leads to disruption in connective tissue of the skeleton, eyes, and CV system
    • Mutations are point or frameshift
40
Q

features of marfan syndrome

A
  • Skeletal
    • Long limbs, fingers, and toes
    • Hyperextensible joints
    • Deformed chest
  • Eyes
    • Dislocated lenses due to lax suspensory ligaments in the eye
  • Cardiovascular
    • Aortic dilation with valve regurgitation and aneurysm (dissecting)
41
Q

etiology and characteristics of cri du chat

A
  • Partial deletion disorder (46, XY deletion of 5p)
  • Characteristics
    • Cat like cry as infants
    • Low birth weight
    • Hypotonia
    • Feeding difficulties with failure to thrive
    • Microcephaly
    • Micrognathia
    • Clumsiness
    • Hyperactivity
    • Moderate to severe cognitive impairments
42
Q

prader willi etiology

A
  • Differential activation of genes depending on the parent from whom they are inherited
  • Deletion of 3-4mb of chromosome 15
  • Inherited from the father
43
Q

prader willi characteristics

A
  • Fetal
    • Decreased activity
  • Infancy
    • Failure to thrive
    • Respiratory and feeding difficulties
    • Severe hypotonia
  • By 2 y/o
    • Excessive eating may start
    • Obesity becomes a concern
    • Tone improves with walking typically achieved by age 2
  • Behavioral issues
    • Temper tantrums
    • Stubbornness
    • Obsessive compulsiveness
  • Cognition ranges from low normal to severely impaired
44
Q

etiology of angelman’s syndrome

A
  • Differential activation of genes depending on the parent from whom they are inherited
  • Deletion of 3-4mb of chromosome 15
  • Inherited from the mother
45
Q

characteristics of angelman’s syndrome

A
  • “Happy Puppet Syndrome”
  • Puppet like gait
  • Subtle dysmorphic facial features
  • Frequent and inappropriate laughter
  • Ataxia
  • Seizure disorder
  • Sleep disorder
  • Love water
46
Q

etiology and characteristics of williams syndrome

A
  • Etiology
    • Disturbance in the elastin gene
  • Characteristics
    • Cardiovascular disease
    • Elfin like face
    • Wide mouth with full lips
    • ADHD
    • Learning disorder
    • Mild cognitive impairments
    • Decreased visuospatial skills
    • Early joint laxity with later compensations
    • Sensory defensiveness
    • Musically talented
47
Q

incidence and etiology of fragile x syndrome

A
  • Incidence
    • Leading hereditary cause of developmental learning disorders
      • 1/2000 boys will be affected
      • 1/4000 girls will be affected
  • Etiology
    • Expansion of a CGG repeat in FMR1 gene leads to gene inactivation
48
Q

characteristics of fragile x syndrome

A
  • Normal structure
  • Broad forehead
  • Elongated face
  • Large prominent ears
  • Strabismus (crossed eyes)
  • Highly arched palate
  • Hyperextensible joints
  • Hand calluses (from self abuse)
  • Pectus excavatum (indentation of the chest)
  • Mitral valve prolapse (benign heart condition)
  • Enlarged testicles
  • Hypotonia
  • Soft, fleshy skin
  • Flat feet
  • Seizures (in about 10%)
49
Q

incidence of rett syndrome

A

Occurs almost exclusively in females (males tend not to survive

50
Q

disease course of rett syndrome

A
  • Progressive
  • Typical prenatal and perinatal period with normal development up to 6-18 months
    • May see mild hypotonia, placid personality, and a weak suck/cry during this time
  • Head circumference normal at birth
    • Decelerates anywhere from 3-48 months
51
Q

What occurs during the short period in which development stagnates followed by rapid regression in motor, language, and psychosocial functions of rett syndrome

A
  • Loss of purposeful hand motions (replaced with characteristics hand wringing)
  • Gait and truncal ataxia
  • Tremors
  • Apraxia
  • Autistic like behavior
  • Bruxism
  • Breathing irregularities (hyperventilation or episodic apnea)
  • GERD
  • Impaired bowel mobility
  • LE vasomotor changes
52
Q

disease course of rett syndrome

A
  • Fits of screaming/crying common by 18-24 months
  • Severely impaired language skills and cognition, seizures
  • After a rapid deterioration, the disease becomes somewhat stable
  • Dystonia results in hand and foot deformities and kyphoscoliosis
  • Osteoporosis occurs early
53
Q

etiology and characteristics of neurofibromatosis

A
  • NF1 (neurofibromatosis type I) gene is a player in signal transduction
  • The NF1 is considered a tumor suppression gene
  • A point mutation in this gene leads to loss of cell differentiation and uncontrolled growth
  • Characteristics
    • Café au lait spots
    • Fibromas
    • Lisch nodules in the eye

Special Pops (Review Q's/Re-outlined PPT) (24 decks)

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