Genetics Flashcards
Dysmorphology (3)
- Aspect of clinical genetics that involves the syndrome diagnosis in children who have unusual facial features, congenital malformations and often have associated cognitive and motor delays.
- > 3500 syndromes
- Some are instinctive recognized by past experience, others involve pieces of puzzles
Cleidocraniodysostosis
rare; abnormal pelvis, unable to delivery babies as a female
Blaschko’s Lines
fine lines that occur from back to the front that may cause a pigment difference; clinical expression of generalized altered stout
- May see neurocutaneous disorders following the lines of Blaschko’s
- Lines of normal cell development in the skin
Chromosomal Disorders (3)
- Part or whole chromosome is missing or duplicated
- Example: Down syndrome
- Tested by Karyotype
Microdeletion or microduplication syndromes (4)
- A very small piece of chromosome is missing or duplicated
- Cannot be seen on karyotype
- Examples: DiGeorge, velocardiofacial; williams syndrome
- Tested by Fish/ Array comparative hybridization (ACGH)
Single Gene Disorders (6)
- A mutation in a single gene causing a disorder
- Dominant (AD), recessive (AR), X-linked
- AD: Marfan syndrome, neurofibromatosis, type 1
- AR: cystic fibrosis, sickle cell disease, Tay Sachs disease
- X-linked: Duchenne Muscular dystrophy
- Testing: Mutation analysis, DNA sequencing and or deletion testin
* Usually micro-array
Triplet Repeat Disorders (4)
- Trinucleotide repeats in certain genes exceeding the normal, stable threshold which differences for each gene.
- Results may be interference of the normal gene or gene product
- Example: Fragile X, Huntington disease
- DNA tests for number for repeats
* Male child that will have significant developmental delay
Variable Penetrance
When two patients with the same disorder that don’t have the same clinical manifestation (ex: Turner Syndrome, Marfan’s Syndrome); how the gene is expressed in a patient
Ex: Some children with Down Syndrome can be very high functioning and some aren’t even able to talk (low functioning)
Multifactorial Disorders (3)
- A combination of genetics and environment
- Examples: Cleft lip and palate; clubfeet; pyloric stenosis
- No current testing available
Epigenetic Disorders (3)
- Changes are not in the sequencing but in the expression of the DNA
* Changes in expression but not sequencing - Examples: Prader Willi; Beckwith-Weidman syndrome
- Testing by Methylation analysis
Diagnosing Genetic Diseases (4)
- Informs reproductive decision
- Preventative strategies
- Explanation of what you can do
- Massive parallel sequencing will explain what is causing the patient’s problem
* Take an 11 year old who has a sudden cardiac arrest; Genome would tell the patient’s need for implant
Sequences
A defect occurs and subsequent development is abnormal
VACTERLS ASSOCIATION
V -- vertebral anomalies / dysgenesis, vascular anomalies A -- anal atresia C -- Cardiac anomalies T -- trachea-esophageal (T-E) fistula E -- esophageal atresia R -- renal anomalies, radial dysplasia L -- Limb anomalies S - Single umbilical artery
CHARGE ASSOCIATION
C" for coloboma "H" for heart defects "A" for atresia choanal "R" for retardation of growth and development "G" for genitourinary problems "E" for ear abnormalities
Complexes
Abnormalities in adjacent structures; something occurs on one side of the face and may cause the rest of the face to cause an anomaly
Goldenhar syndrome (6)
- Affects one side of the face only. :
- Partially formed or totally absent ear (microtia)
- Chin may be closer to the affected ear
- One corner of the mouth may be higher than the other
- Benign growths of the eye
- Missing eye
Major Anomalies (2)
- Easily identified
2. Involve easily identified malformations
Congenital Anomalies (2)
- Present at birth
2. Does not imply cause
Minor Anomalies (3)
- Physical difference that occur in fewer than 4% of the population
*if they occur in more than 4% then it is normal phenotypic variation
Ex: specific creases are found on Asian children as a normal phenotypic indication … epicanthial folds found in Asian children greater than 4% of the time - More commonly in areas that are more variable and complex: face, hand
- 70% in these two area
Types of Minor Anomalies (5)
- Some minor anomalies are markers for occult major malformations
- Sacral tuft of hair or deep sacral dimple: associated with occult spinal dysraphism
- Many genetic syndromes are specific patterns of minor anomalies occurring together
- Specific minor abnormalities of face, hands, feet: Down syndrome
- Three or more minor anomalies increased risk of having major malformation –> Assess for major malformation
Most common external anomalies are in the… (4)
- Face
- Auricle
- Hands
- Feet
Recognition of Minor Anomalies (3)
- Some minor anomalies run in families as a single variation; As high as 14% of newborns have at least one minor anomaly.
- If there are three or more minor anomalies, there is approximately a 20% chance of a major anomaly.
- Represent deformation due to altered mechanical forces affecting the development of otherwise healthy tissue
* Very common to have minor anomaly; some are just developmental deformations that are not an issue
Normal Phenotypic Variants (10)
- Saddle (mildly upturned nose)
- Mild to moderate in bowing of lower leg
- Sacral dimple, not deep
- Mild syndactyly of second and third toes
- Toenail hypoplasia in the newborn
- Hydrocele of the testicle
- Epicanthal folds
- Unilateral epicanthal fold is indicative of torticollis
- Slanting of the palpebral fissures
- Brushfield spots (20% of normal newborns)
Frequent Newborn Findings (2)
- Normal Phenotypic variant
- STORK BITES: Fine non-elevated pink to red capillary hemangioma at nape of neck, over central forehead and eyelids and in the lumbosacral region
Skull Physical Assessment Findings that may be significant (5)
- Asymmetrical head or face
- Brachycephaly (high hat)
- Flattened occiput
- Fontanels too large or small
- Overlapping sutures (risk with Craniocyostosis)
Brachycephaly
most likely do to closure of coronal or lamboidal (or both) sutures
head shapes (3)
- Triangular shape – metopic suture or frontal suture closed prematurely
- When saggital suture closes prematurely – long narrow
- When coronal or lamboidal sutures closes prematurely – Brachycephaly
Facial Proportions (3)
- Micrognathism: small mandible
- Retrognathism: Receding
- Prognathism (Projection of jaw beyond that of forehead)
Minor Anomalies of the Face (13)
- Ocular hypertelorism ( A low nasal bridge will give the appearance of hypertelorism
- Telecanthus is consequence of lateral displacement of the inner canthi
- Synophrys
- Fused eyebrows
- Flat bridge of nose
- Hypotelorism
- Anteverted nostrils
- Epicanthal fold
- Iris freckles
- Upward palpebral slant (mongoloid slant)
- Downward palpebral slant (antimongoloid slant)
- Blue sclera
- Different eye colors