Topic 6 Part 2 Adult onset genetic conditions

Question 1

_ is a risk factor for diseases throughout all stages of life.

Answer 1

Family history.

Question 2

Anticipation

Answer 2

1. Symptoms of a genetic disorder become apparent at an earlier age as the disease passes from one generation to the next.
2. Example: Huntington disease manifests at 55 years of age in the first generation, 50 years of age in the second generation, and 40 years of age in the third generation.

Question 3

Huntington disease (HD)

Answer 3

1. Autosomal dominant; diagnosed by greater than 40 CAG repeats in the huntingtin gene on chromosome 4.
2. Adult onset (usually in the 40s) - diagnosis requires psychological counseling because this is a fatal disease.
3. Causes accumulation of cholesterol in the brain and premature death of brain cells.
4. Symptoms: Chorea (uncontrollable, writhing movements); loss of motor control, gait, and function; serious dementia, depression, paranoia - leads to suicide risk.

Question 4

Genetic hemochromatosis

Answer 4

1. Autosomal recessive; mutation in the HFE gene on chromosome 6 leads to “iron overload” due to increased iron absorption and storage.
2. Usually diagnosed in the 50s, more common in individuals of European descent. 1 in 300 people affected; 1 in 9 are carriers.
3. Early signs and symptoms: Fatigue, joint/abdominal pain.
4. Treatment: Removal of at least 500 mL of blood every 3-4 months. Restriction of iron and vitamin C intake. No raw oysters due to presence of iron-thriving organism.

Question 5

Gaucher disease (type 1 adult)

Answer 5

1. Autosomal recessive; lysosomal storage disorder caused by lack of enzyme to metabolize fatty substances.
2. Cells with accumulated glucosylceramide invade the spleen, liver, and bones.
3. Phenotype: Fatigue, anemia, bruising, nosebleeds, pain. Unlike in the pediatric type, in the adult type there is no brain involvement.
4. Management: Pain reduction therapies, blood transfusions, orthopedic surgery for bones and joints, possible splenectomy.

Question 6

Huntington disease is diagnosed through _ testing.

Answer 6

Presymptomatic predictive.

Question 7

Genetic hemochromatosis can be diagnosed by examining the serum levels of _

Answer 7

Transferrin and ferritin (both will be elevated).

Question 8

Examples of multifactorial adult onset disorders

Answer 8

Diabetes, hypertension, coronary heart disease, cancer, Alzheimer disease, schizophrenia, addictions.

Question 9

“HuGE” database

Answer 9

1. Human Genome Epidemiology.
2. Goal is to establish an information exchange that promotes global collaboration in developing peer-reviewed information on the relationship between human genomic variation and health and on the quality of genetic tests for screening and prevention.

Question 10

Breast cancer risk categories

Answer 10

1. “Average” risk (all women): Mammograms starting at age 40 and yearly after 50; BSE and clinical breast exams.
2. “High” risk (positive family history for breast cancer): Test for BRCA1 and BRCA2 mutation.
3. “Extremely high” risk (positive for BRCA 1 or BRCA2 mutation): Consult for prophylactic surgery.