Infancy Lecture Flashcards
Define karyotypic abnormalities
Chromosomal
- Present in ~ 10-15% of live-born infants with congenital malformations
Downs –> Klinefelter (XXY)–> Turners (XO)–> Trisomy 13
Define single-gene mutations of large effect
Relatively uncommon but follow mendelian patterns of inheritance
Define multifactorial
Ineraction of two or more genes of small effect with environmental factors
Down Syndrom
Major cause of mental retardation 80% have IQ between 25-50 1-2% mosaicism (chromosome divided unevenly) Translocation Maternal age has strong influence
Failure of chromosomes to separate properly during meiosis I?
Zygotes= 2 triomic, 2 monosomic
Failure of chromosomes to separate properly during meiosis II?
Zygotes= 1 trisomic, 1 monosomic and 2 normal
Chromosome 21 contains?
Approximately 430 genes
- Several gene clusters –> participate in the same pathway
Define the gene dosage hypothesis
- Phenotypica features related to over expression of genes
- Others have variable degrees of change in expression
- Presence of miRNA genes on 21 that can shut down genes elsewhere in the genome
What are clinical features of down syndrome?
Congenital heart disease Atrial septal defects Valve malformations Septal defect Acute leukemia Neurpathologic changes Abnormal immune responses
Define environmental causes
Malformations resulting from environmental factors are related to the timeing of the intrauterine exposure and teh differential suceptibility of various organ systems
What is cytomegalovirus?
Most common
- Highest risk for malformations in second trimester
Affects CNS –> mental retardation, microcephaly and deafness
What is rubella?
Infection before 16 weeks gestation
Results in cataracts, heart defects and deafness
Define perinatal infections
Infections of embryoe, fetus, and neonates
Define transcervical or ascending infections
- Caused by bacterial and viral infection saquired via cervicovaginal route
- Inhalation into the lungs
- Through infected birth canal
Define transplacental or hematologic infections
Caused by mostly parasites and viral infections and a few bacterial infections
Gain access to the fetal bloodstream via chorionic villi
– Any time during gestation
– At time of delivery
Drugs and chemicals as causes?
Cause less than 1% of congenital malformations
Agents suspected to be teratogenic include: thalidomide, folate antagonists, androgenic hormones, alcohol, anticonvulsant, and accutane
Radiation as a cause?
Exposure to heavy doses during organogenesis
- Results in microcephaly (small head), blindness, skull defects, spina bifida (incomplete closure neural tube)
What is the mechanisms of malformations
Timing of prenatal teratogenic insult: occurrence and type of malformation; different times
Level of Actions: may act on cell proliferation, migration, differentiation, and damage to formed differentiated organs
Directly or inluencing other genes: morpogenesis genesis
Define congenital heart disease
Abnormalities of the heart that are present from birth
- Arise from faulty ebryogenesis during gestational week 3 to 8
Causes of congenital heart disease?
Result from chromosomal abnormalities or environmental factors and maternal illness
— Abnormal shunting of blood
Tetralogy of Fallot involves?
- A ventricular septal defect, a hole between the two bottom chambers of the heart
- The pulmonary trunk is narrowed so that muss less than normal amounts of blood pass from right ventricle into the lungs
- Reght ventricle is more muscular than normal
0 Aorta is positioned over the ventricular septal defect instead of in the left ventricle (low oxygenated blood)
