Clinical Disorders

Question 1

Down Syndrome:

• What is the chromosomal abnormality?
• What is the most common cause of the above abnormality?
• Qualitative frequency?
• Common signs and sx?

Answer 1

• Trisomy 21
• Maternal age (additional chromosome contributed by nondysjunction in the mother).
• Most common form of trisomy compatible with live birth.
• Sx: Mental retardation (range), Distinct facial characteristics, GI tract obstruction, Congenital heart defects, Single horizontal palmar crease, Increased risks for respiratory infection and leukemia, Alzheimer-like sx later in life, Male sterility, Eye abnormalities, Hearing loss.

Question 2

Edward Syndrome:

• What is the chromosomal abnormality?
• What is the most common cause of the above abnormality?
• Qualitative frequency?
• Common signs and sx?

Answer 2

• Trisomy 18
• Maternal age (additional chromosome contributed by mother due to nondisjunction).
• Most common chromosomal abnormality among stillborns. 50% die in fist month and 90% die within 1 year. (Survival indicative of mosaicism/mitotic error)
• Sx: SGA, Severe mental retardation, Clenched fist, Congenital heart defects, Short sternum, Developmental retardation, Kidney defects, Diaphragmatic hernia, Overlapping fingers, Small eyes/mouth, Small receding jaw, Malformed ears, Short big-toe that bends up, Omphalocele

Question 3

Patau syndrome

• What is the chromosomal abnormality?
• What is the most common cause of the above abnormality?
• Common signs and sx?

Answer 3

• Trisomy 13
• Maternal age is sig. factor.
• Sx: Cleft lip/palate, Postaxial polydactyly, Mental retardation, Deafness, Developmental retardation, Small abnormal eyes, Small triangular nose, Small head.

Question 4

Turner syndrome

• What is the chromosomal abnormality?
• What is the most common cause of the above abnormality?
• Frequency of live births vs. Spont. Abortions?
• Common signs and sx?

Answer 4

• 45, X
• 80% due to meiotic nondisjunction in father (X-Y synapsing during meiosis leads to more frequent nondysjunction than X-X).
• Rare in live births but 15-20% of chromosomal abnormalities in spont. abortions.
• Sx: Lack of sexual development, Short stature, Webbed neck, Bent forearms, Triangle shaped face, Ovarian dysgenesis, Kidney abnormalities, Lack of growth spurt.

Question 5

Kleinfelter Syndrome

• What is the chromosomal abnormality?
• Common reason for clinical presentation?
• Common signs and sx?

Answer 5

• 47, XXY
• 1/20 males in fertility clinics are 47, XXY.
• Sx (more subtle): Tall stature with long limbs, Sterility, Androgen deficiency, Learning deficiency, Gynecomastia, Poorly developed secondary sex characteristics, Small testes.

Question 6

Trisomy X (47, XXX)
Common Signs and Sx?

Answer 6

Few abnormalities. Sterility, Menstrual irregularity, Mild mental retardation.

Question 7

47 XYY

• Common Signs and Sx?
• Misnomers?

Answer 7

• Taller than average men, Slight IQ reduction, ADD is common.
• Incorrectly believed to predispose violent behavior.