Genetic Disorders Flashcards
What are the 3 chromosomal disorders?
Trisomy 21: Down Syndrome
Trisomy 18: Edwards Syndrome
Trisomy 13: Patau Syndrome
What is non-disjunction?
During cell division and mitosis, two chromosomes go to one cell. They staged together and now the cells have an extra 21 chromosomes.
What is translocation?
Early on after fertilization and the most common reason why we end up with a trisomy. The chromosome can break off and stick on another chromosome.
What is mosaicism?
Happens later in cell division. Same error as non-disjunction, but it is occurring later. We see a less severe presentation.
Is there an increased risk of Down Syndrome with maternal age?
Yes
Clinical picture of Down Syndrome.
Small stature, upward slant of eyes, wide gap between toes 1 and 2, micrognathia, small oral cavity resulting in protruding tongue, speckling of iris, epicanthal fold at eyes, saddle nose, small ears, and short broad hands with palmar crease.
Neuropathophysiology of Down Syndrome.
Simplicity in convolutional pattern, reduced synaptogenesis, lack/delay of myelination, decreased number of small neurons, structural abnormalities of neurons, and increased number of neurofibrillary tangles and senile plaques.
What is microbrachycephaly, and what genetic disorder is it associated with?
Flattening of the skull from A-P, so it is wider M-L. This is associated with Down Syndrome.
MSK picture of Down Syndrome.
Hypotonia, muscular variations, foot deformities, hip subluxation/dislocation, patellar instability, scoliosis, and A/A instability.
Sensory deficits of Down Syndrome.
Hearing loss, strabismus, cataracts, chronic otitis media, nystagmus, and myopia.
What are the 3 ways to diagnose Down Syndrome?
Karyotype pre/postnatal: amniocentesis
Alpha-fetoprotein
Observation at birth
What does AFP stand for? What genetic disorder is it associated with and what does it mean?
Alpha-fetoprotein: blood test from the mother, typically during the second-trimester. They could identify the amount of AFP. In Down Syndrome, the levels of AFP are abnormally low.
What is amniocentesis?
Large needle through the abdomen, through the uterus, and withdraw amniotic fluid surrounding the baby. The increased risk could cause the mother to go into labor. Analyzing the cells of the baby that would be floating in the fluid and seeing if the trisomy is present.
Is Edwards Syndrome correlated with advanced maternal age?
Yes
Clinical Picture of Edwards Syndrome.
LBW, small stature; CV/GI/urogenital/skeletal malformations; long/narrow skull, low set/misshapen ears, tone abnormalities, profound MR; neuropathy.
What genetic disorder is associated with a long A-P and narrow M-L shaped head?
Edwards Syndrome
Clinical Picture of Patau Syndrome.
CNS/CV/MS/urogenital malformations, severe/profound MR, anophthalmia/microphthalmia.
What are sex chromosome disorders?
Turner syndrome, Klinefelter syndrome, and Fragile X syndrome.
What is Turner Syndrome? Is it correlated to maternal age?
Extra or missing sex chromosome. There is NO correlation to maternal age.
What are some physical features of Turner Syndrome?
Webbed neck, cubital valgus, dorsal edema of hands and feet, hypertelorism, epicanthal folds, ptosis, elongated ears, and growth retardation.
What are some systemic features of Turner Syndrome?
Congenital heart disease, kidney malfunctions, hearing loss, decreased gustatory and olfactory, deficits in spatial perception and orientation, average intellect in most, and sexual infantilism.
What are some skeletal abnormalities of Turner Syndrome?
Hip dislocation, foot deformities, osteoporosis, and idiopathic scoliosis.
What is Klinefelter Syndrome? What is the clinical picture?
Two x chromosomes and one y, male. Testes fail to enlarge, gynecomastia, normal IQ, and sterility.
What is Fragile X Syndrome? What are some clinical features?
Structural abnormality of X chromosome; large head/ears/jaw, myopic, v-shaped palate, large testes, and active/autistic.
