Need Explanations to NBME 19! Help Please.... - blessedalways

[ArchivalUser]

12- Do you know what is the dx here?

[ArchivalUser]

Hey, for #12 the diagnoses is Hepatitis B Virus and the answer is hepatocytes. In fact you can tell by the signs and symptoms that the patient has and by the lab values. For instance according to Medscape, HBV can cause signs and symptoms such as the following:

*Anorexia
*Nausea
*Vomiting
*Low-grade fever
*Myalgia
*Fatigability
*Disorder Gustatory Acuity
*Smell sensations (aversion to food and cigarettes)
*Right upper quadrant and epigastric pain (intermittent, mild to moderate) etc.

In addition, the elevated bilirubin represents jaundice and both the AST and ALT are elevated, which is common in the HBV lab values. Also, the serology test shows positive on the HBeAg, HBsAg, HBV-DNA, and the IGM anti-hepatitis B core antigen. Moreover, the liver biopsy does have cytotoxic T cells mediated damage because the further observation on this question said that "CD8+ T lymphocytes bind to antigens, resulting in liver injury".

[ArchivalUser]

you got it. yes it is Hepatitis due HBV infection.
It is important to note that the damage to the hepatocytes is done by the CD8+ T lymphocytes and not by the virus itself. Viral antigen is preesnted by MHC class-I on the surface of infected hepatocytes.

[ArchivalUser]

Thanks

[ArchivalUser]

14- What about it?

15-
Karyotyping is normally done on a blood sample
This girl must have received a bone marrow from a MALE Donor.
So if she got a bone marrow from a male donor, all the blood cells producing from it will have 46 XY, and this is what will show on the karyotyping on her blood sample. If we take her skin sample and do the karyotype on it, it will still be 46 XX though.

[ArchivalUser]

16- Propronalol is nonselective beta blocker that blockes Beta-1 and Beta-2 receptors

Beta -1 receptors blockade on heart cells will decrease CO.
Beta - 2 receptor blackade on blood vessels will prevent vasodilation, allowing the vasoconstriction to predominate, this will increase TPR.

[ArchivalUser]

17- What do you think is the most likely dx?

[ArchivalUser]

18-Respiratory response to Rib fracture:

Respiratory rate ----- Increased
Tidal volume --------- Decreased
Airway resistance---- no change

In order to avoid pain upon taking deep breaths, patient will have shallow breathing (decreased tidal volume) and the respiratory rate will increase to compensate low tidal volume in order to maintain normal minute ventilation.

So in order to avoid pain ------ “Shallow, rapid breathing”
(decreased TV and increased RR)

[ArchivalUser]

19-just gogle image for "Lung Abscess x-rays". This is what i did for all other relevant x rays, printed them and attached to my notes.

[ArchivalUser]

20-

Probability of man being carrier = 2/3 (i assume you already know why)
Probability that the man will transfer the gene = 1/2

In order to calculate the woman's probability of being a carrier, we use Hardy-W Equation.

q2 = 1 /40,000
q = 1 / under sqr of 40,000
q = 1/200

Carrier frequency = 2pq
= 2 x (1/200)
= 2/200
= 1/100

Probability of woman being carrier = 1/100
Probability that the woman will transfer the gene = 1/2

Probability that the child will be affected (just multiply all the probabilities)

2/3 x 1/100 x 1/2 x 1/2 = 2 /1200 = 1/600