Scene II: Will Alan ever play for the Lakers?

After this lesson, the students will be able to:

1) Explain x-linked inheritance using Factor VIII deficiency (hemophilia) as an example;

2) Describe the treatment for hemophilia;

3) Explain the importance of early diagnosis and carrier testing of hemophilia; and

4) Describe some societal issues associated with hemophilia and its treatment.

Alan’s Situation

Alan suffers a painful knee injury while shooting baskets in his parents’ driveway. Examination at the emergency room indicates that Alan has a bad sprain, in addition to bleeding within the knee joint. Further testing reveals a deficiency of Factor VIII, and a diagnosis of hemophilia is made. Stacy is found to have reduced Factor VIII levels, consistent with her being a hemophilia carrier.

Alan’s Situation (contd.)

XH Xh XH Y

The gene for Factor VIII is on the X chromosome. Hemophilia is a sex-linked disorder.

Stacy, since you’re a carrier you must have one X chromosome that produces factor VIII and once that does not.

It’s a good thing you have a “back up” X chromosome or you would also have hemophilia.

Paul, since you have no history of hemophilia and you have normal factor VIII, your only X chromosome is fine.

But since Alan is a boy he received your Y chromosome.

Stacy, Alan must have inherited your X chromosome that does not make factor VIII. He has “no back” X chromosome. His disorder has gone unnoticed all these years until his basketball injury.

What is Hemophilia?• AKA: Factor VIII

deficiency• Blood clotting disorder

usually affecting males– 1 in 5,000

• Abnormal protein “Factor VIII” created– Factor VIII necessary

for blood clotting– Clotting takes longer

• Severity varies based on amount of Factor VIII produced

• Sex-linked disorder (found on X chromosome)

Healthy girl Healthy boy

Healthy girl (carrier)

hemophiliacboy

Key:H = healthyh = hemophilia

Just for practice: Kelly is a healthy carrier of hemophilia, but Jim suffers from the disease.

What is the probability of getting a:

Healthy son?

25%

Healthy daughter?

25%

Child with hemophilia?

50%

Carrier child?

25%

Healthy girl (carrier)

Healthy boy

Disease girl Disease boy

Treatments• Factor VIII Replacement:

– Intravenous injections of Factor VIII

– Causes clotting

• Joint Replacement– Knee, hip, ankle

replacement if arthritis is severe

• Regular exercise for strong muscles to protect the weak joints

Alan’s Situation

Alan is starting on Factor VIII home infusion. His parents are taught how to inject Alan with Factor VIII that has been removed from donated blood, purified, and packaged for use.

The Factor VIII can be kept at home and prepared for injection when Alan feels that bleeding has occurred. The Factor VIII can also be taken with them on trips.

Factor VIII Infusions

• Objective: replace missing clotting factor

• When used:

– Used at time of bleeding to prevent tissue damage

– Prior to and during surgery

• Cost: over $100,000/year (beyond lifetime cost of many insurance plans)

• Prior to 1984: HIV prevalent in the Hemophilia community (70-90%)

Alan’s SituationAfter the increased risk of hepatitis is discussed,

immunizations against Hepatitis B and D are scheduled.

What about AIDS? If Factor VIII comes from donated blood, can he catch

AIDS?

Let’s see if our insurance will pay for Factor

VIII.

AIDS was a threat to hemophiliacs years ago, but more strict donor guidelines and heat-treating of blood reduces the chances of AIDS being a problem.Well that’s

reassuring.

Alan’s SituationSeveral parents

demanded that the boy be removed from school, threatening to remove their own children if their demands were not met.

Stacy remembered following the issue in the newspapers, but she took no particular position on the issue.

I remember that boy in

Frank’s school who

had HIV about a year ago.

He got HIV from a blood transfusion during heart

surgery.

What must it have been like for the boy and his

family?

Expanding the Chance FamilyStacy, since hemophilia is X-linked and you’re a carrier, it’s important that we contact other family members of yours to discuss their risk of being carriers. Do you have any sisters?

Yes, one. And a brother, David.

Your sister might also be a carrier. You should bring her up to date on this and ask her to make an appointment with us.

Absolutely NOT! And if you tell her anything about Alan’s hemophilia, I’ll sue you and this place for everything you’re worth.”

Chances’ Choices Essay #2:

Does Martha’s right to know about her risk of being a hemophilia carrier take precedence over Stacy’s right to keep her family’s medical records confidential?

• Essay Format:

– Ink or typed (no pencil)

– Add title and date

– Minimal length = ¾ page

– If typed: 1” margins, 12-point times new roman font, double spaced.

– Complete essays (Introduction, body, conclusion)

– Spellcheck and proofread