Practice 2

Question 1

If a patient presents with ptosis, diplopia, fatigable chewing, and dysphagia, then they are most likely to have what neuromuscular disorder?

Answer 1

Myasthenia gravis (autoab to post-synaptic ACh R)

Presents with weakness of the eye and bulbar muscles that worsen with prolonged activity.

Question 2

Rb is on what Chr?

Answer 2

13

• since Rb is a tumor suppressor protein both copies need to be lost for tumorigenesis to occur.

Question 3

Why does sporadic retinoblastoma occur with unilateral vision loss, while hereditary retinoblastoma affects both eyes?

Answer 3

Knudson 2 hit hypothesis = need both copies to be affected for tumorigenesis.

sporadic Rb = 2 spontaneous somatic mutations in a single cell.

Hereditary Rb = only need 1 spontaneous mut, this is why you can have other primary malignancies like osteosarcoma with the inherited form.

Question 4

Why do DiGeorge patients develop tetany?

Answer 4

No PTH gland because no parathyroid gland develops..

Failed development of 3rd and 4th pharyngeal pouches.

Question 5

If a patient presents with severe leukocytosis, sterile abscesses, delayed cord separation, and poor wound healing, then what would be the most likely Dx?

Answer 5

Defect in beta-2 integrin (adhesion molecule). Prevents Macs from migrating across the endothelium.

Question 6

If you had impaired function and production of CD3+ and CD20+ cells, then what enzyme is most likely deficient?

Answer 6

Adenosine deaminase deficiency&raquo_space; impaired function and production of CD3+ T cell and CD20+ B cell. Also allows for buildup of toxic adenosine and deoxyadenosine within lymphocytes.

Question 7

Inheritance pattern of Hyper IgM syndrome:

Answer 7

X linked.. Defect in T cell CD40 ligand expressed by T cell&raquo_space; prevents B cell class switching from IgM to other Ab.

Question 8

Characterize the metabolic derangements of DKA in terms of blood [ ] of glucose, K and H+:

Answer 8

Metabolic derangements of DKA include metabolic acidosis, ketonemia and ketonuria, hyperglycemia and glucosuria, hyponatremia, hyperkalemia (K/H exchanger), and hypovolemia.

Hyperammonemia may also be seen due to muscle breakdown.

Question 9

Is spina bifida cystica assoc with Chiari type I or type II malformation?

Answer 9

Chiari Type II

Spina bifida cystica (myelomeningocele) = neural tube defect that causes protrusion of the spinal cord and meninges through an unfused portion of the vertebral column.

Question 10

What’s the diff between syringobulbia vs syringomyelia?

Answer 10

Syringomyelia = fluid filled cavity within spinal cord

Syringobulbia = fluid filled cavity within lower brainstem (medulla).

Both are assoc with Chair Type I

Question 11

What drug do you need to give before removing adrenal gland in Pt with pheochromocytoma?

Answer 11

Phenoxybenzamine - irreversible long acting alpha blocker, prevents peripheral vasoconstriction.

• If you don’t and the pheochromocytoma leaks out during surgery you could have severe vasoconstriction and life threatening hypertensive crisis due to unopposed a1 AR agonism.

Question 12

Preterm infants are at an increased risk of intraventricular hemorrhage if what structure is damaged?

Answer 12

germinal matrix. This is a dense cellular and vascular layer of the subependymal zone of the brain that where neurons and glial cells develop in utero. Lacks structural support so it is vulnerable to spontaneous hemorrhage.

Normally involutes by 28 wks, so is only really a problem in preterm infants.

Question 13

What serious adverse event do you have to look out for when using cisplatin?

Answer 13

ototoxicity. 74-100% of Pt receiving cumulative doses of 200mg can have hearing loss.

Question 14

Slowly progressive dyspnea, fever, cough, and patchy interstitial infiltration are characteristic features of inflammation and fibrosis due to use of what antiarrhythmic drug?

Answer 14

amiodarone (class III antiarrhythmic, K+ channel blocker)

Effects reversible on discontinuation of use.

Question 15

Why is misoprostol sometimes added to the treatment list of a patient on chronic NSAID use?

Answer 15

Misoprostol = PGE1 analog. Helps simulate gastric parietal epithelial cells to produce mucus, and appears to decrease parietal cell acid secretion.

Helps in chronic NSAID use because Cox1 is usually destroyed by NSAIDs, so no endogenous prostaglandins can form, leaving gastric mucosa to have little protection from stomach acid.

Question 16

Why can you have polyp formation with aspirin use?

Answer 16

Aspiring = irreversible COX inhibitor. Causes ^ diversion of membrane phospholipid metabolism towards 5’ lipoxygenase pathway&raquo_space; ^ leukotriene formation (proinflammatory mediators)

Rx = leukotriene modifying agents (monelukast, zafirlukast)

Question 17

Majority of cancers in the head and neck are what type of cancer?

Answer 17

Squamous cell carcinoma (normally due to smoking and alcohol). Dangerous because of local metastasis fo cervical LN or distal metastasis to mediastinal LN

Question 18

Why can diff family members with marfan’s syndrome have very diff phenotypes of the disease?

Answer 18

Although Marfan’s is autosomal dominant (FNB1) it demonstrates variable expressivity (can show diff phenotypes even though genetic mutation is the same)

Question 19

In patients with pseudohypoparathyroidism type I, there is an end organ resistance to PTH due to a defective Gs protein alpha subunit. What are the gross anatomical manifestations of this disease?

Answer 19

short stature, short metacarpal and metatarsal bones.

Autosomal dominant mut in GNAS1 gene.

Question 20

What intracellular molecule is responsible for intron removal from mRNA?

Answer 20

snRNP

Question 21

Hemochromatosis is an autosomal recessive Dz characterized by excessive GI absorption of iron. Common manifestations include liver Dz with hepatomegaly, DM secondary to pancreatic islet destruction, hyperpigmentation (bronze DM), and cardiomyopathy. How would you treat this?

Answer 21

Repeated phlebotomy. Chelation with defrasirox, deferoxamine, and oral deferiprone.

Question 22

Elevated ACTH along with hypotension, hypoglycemia, hyponatremia, and hypokalemia are characteristic of what endocrine disorder?

Answer 22

Primary adrenal insufficiency (Addison’s Dz)

Question 23

Why do you have splenomegaly with cirrhosis?

Answer 23

In cirrhosis, hepatocyte necrosis and extensive fibrosis&raquo_space; distortion of the hepatic vascular bed&raquo_space; portal HTN. The portal venous system is valveless so portal HTN causes retrograde blood flow away from liver and into splenic vein&raquo_space; congestion of splenic red pulp&raquo_space; splenomegaly

Question 24

Bacteroides fragilis are associated with what kinds of infections?

Answer 24

intraabdominal abscess following abdominal trauma/surgery, endometritis and intraabdominal abscesses following gynecologic procedures

Question 25

Defective gene in achondroplasia (dwarfism)

Answer 25

FGFR3 (autosomal dominant, gain of function, point mutation on the fibroblast growth factor gene) ** FGFR3 normally functions to inhibit cartilage proliferation, particularly in the long bones. Amplified FGFR3 >> restricted chondrocyte proliferation and decreased endochondral ossification.

Question 26

If an infant presents with recurrent bacterial infections of the respiratory tract and normal T cell #s but Low B cell #s, and absence of antibody production, what could be the Dx?

Answer 26

Bruton Agammaglobulinemia (X linked agammaglobulinemia). Defect in BTK (signal transduction molecule) required for B cell maturation. If defective, B cells stay in marrow and Ab aren't produced.

Question 27

How would the RBC of a patient with alpha-thalassemia major appear on histo?

Answer 27

hyphochromic, microcytic.

Question 28

How is testosterone concentrated in the seminiferous tubules?

Answer 28

Sertoli cells induce formation of ABP (androgen binding protein) in response to FSH. ABP binds to testosterone and dihydrotestosterone.

Question 29

Sweating is mediated by the ___ fibers of the sympathetic nervous system. Excessive stimulation of these fibers can cause hyperhidrosis (profuse sweating)

Answer 29

cholinergic postganglionic fibers of the sympathetic nervous system

Question 30

How would you treat hyperhidrosis?

Answer 30

Hyperhidrosis is due to overstimulation of sympathetic postganglionic cholinergic neurons that innervate the eccrine and apocrine glands. Rx = systemic anticholinergics (oxybutynin), local injectable anticholinergics (botox), or surgical sympathectomy.

Question 31

The ___ of the uterus is a vestige of the gubernaculum from embryonic development that projects from the uterus through the inguinal canal and into the labia majora:

Answer 31

round ligament of the uterus

Question 32

How are pH and CO2 levels affected in the setting of pulmonary embolism?

Answer 32

PE >> V/Q mismatch >> hypoxemia >> ^ ventilation rate >> hypocapnia and respiratory alkalosis without significant improvement in hypoxemia. So pH is ^ and there is decreased PaCO2.