Genetic Syndromes Flashcards
all disease is either _____ or _______ or _______
genetic or environmental or a combo of the two
give an example of a purely genetic, environmental and combination disease
- purely genetic → cystic fibrosis, sickle cell disease
- environmental → mercury poisoning
- combination → DM type II, HTN
List the 3 Minimum PT Competencies pertaining to genetics
- appreciate one’s limitations in genetics and expertise – ID need for continuing edu
- understand the psychosocial and ethical implications of genetic service
- know when and how to make a referral
when to make a referral
- History of:
- dysmorphology
- brain malformations
- epilepsy
- abd CT
- EEG
- abnormal tone
- weakness
- motor control, discoordination
- delayed development
- sensory disturbances
- children with global DD (even in absence of dysmorphisms)
What are the 3 types of purely genetic disease
- Monogenic
- Mendelian inheritance, a single gene is involved
- Polygenic
- complex inheritance pattern, many genes are involved
- Cytogenic
- involves large-scale changes in chromosomes
list relevant terms pertaining to genetics
- Gene
- Locus
- Alleles
- Homozygous
- Heterozygous
- Genotype
- Phenotype
define cytogentics
study of chromosomes and their abnormalities
define Karyotype
chromosomes are displayed according to their length
what is FISH?
a technique in which chemically tagged chromosomes specific DNA probes to label a chromosome sequence and visualize it under flourescent microscope
what is an array CGH?
Array Comparative Genomic Hybridization
- compares child’s DNA with a control DNA to ID microdeletions or microduplications
- revoluntionized cytogenic testing
- high diagnostic yield of genomic abnormalities
- this technique is replacing FISH for subtelomere imbalances
List the 4 categories for genetic disorders
- chromosomals
- single gene
- multifactorial
- mitochondrial
briefly describe the category of “chromosomal disorders”
- two subtypes:
- altered in structure or number
- includes:
- deletions, inversions, duplications, translocatoins
- 10-15% of human conceptions
- 1/160 live births
- leading cause of miscarriage
- in general → not hereditary
chromosomal disorders can be due to an alteration in number of chromosomes. List terms assocaited with this
- Polyploidy
- Aneuploidy
- Autosomal monosomy
- Mosaicism
define polyploidy
complete extra set of chromosomes → all of these diseases are lethal
define aneuploidy
absence (monosomy) or duplication (trisomy) of a chromosome in a cell → usually only one chromosme is affected
how often do children with an autosomal monosomy survive?
rarely
define mosaicism
most of these are due to a full trisomy conception followed by loss of extra chromosomes in some cells during mitosis in the embryo
milder clinical manifestation
List general characteristics assocaited with chromosomal abnormalities
- most are assocaited with developmental delay and cognitive impairment
- large number of genes are involved with CNS development
- characteristic craniofacial features
- delayed growth
- congenital malformations
List common autosomal trisomies
- Down syndrome
- Edwards syndrome
- Patau syndrome
nearly all autosomal trisomies are associated with what?
advanced maternal age
Describe Down Syndrome
- Trisomy 21 → most common form
- phenotypic feature → hypoplasia is the most common element of the many phenotypic features
List craniofacial features in Down Syndrome
- 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
List MSK/CT features in Down Syndrome
- Diastasis recti
- joint hypermobility
- atlantoaxial instability w/risk of spinal cord compression
- simian creases
- wide gap between toes 1 and 2
- hypoplasia of the middle phalanx of 5th clinodactyly
- hypoplastic pelvis w/shallow acetabular angle
- linear growth deficits
- greatest between 6-24 months
- mostly due to leg length reduction
- delayed skeletal maturation rate
- 1/3 overweight by age 3
Eyes/Vision and Ears/Hearing features in Down Syndrome
- Eyes
- iris speckling (brushfield’s spots)
- myopia
- nystagmus
- strabismus
- tear duct blockage
- Ears
- conductive hearing loss
- sensorineural hearing loss
- mixed hearing loss (as many as 78%)