Block 24

Question 1

scaphoid fractures can lead to

Answer 1

• avascualr necrosis owing to retrograde blood supply
• its the most commonly fractured bone in wrist
• it should be suspected in any patient with persistant wrist pain and tenderness in the anatomical snuffbox.(between extensor pollicis longus and extensor pollices bravis tendons)

Question 2

Patients with interstitial lung disease have increased expiratory flow rates, why?

Answer 2

-patients with progressive pulmonary fibrosis with thickining and stiffening of the pulmonary interstitium. This cause increased lung elastic recoil as well as airway widening due to increased pulling (radial traction) by the surrounding fibrotic tissue.

Question 3

CGD

Answer 3

Pathogenesis : inactivation mutation affecting NADPH oxidase
- impaired respiratory burst inhibits phagocytic intracellular killing

Clinical:

• recurrent infections with catalase positive bacteria and fungi
• Lung, skin, lymph nodes and liver most commonly involved
• diffuse granuloma formation

Diagnosis:

• measurment of neutrophil superoxide production
• DHR flow cytometry (asses the production of superoxide radical by measiring the conversion of DHR to rhodamine, which is floruscent green compound that can be detected by flow cytometry, cells deficient in NADPH oxidase have decreased fluorescence)
• NBT testing.

Question 4

High arginine in CSF with spastic paresis and failure to thrive

Answer 4

Arginase deficiency, its the enzyme involve in conversion of arginine to urea.

• unlike other urea cycle disorders patients have mild or no hyperammonemia..
• treatment consists of low protein diet.

Question 5

Hawkins test

Answer 5

Involves abduction of the arm by 90˙ angle , while thumb is facing downward and flexion 30˙.

• then a pressure is elicited on the arm, if pain is present its positive
• positive test means there is impingement on the supraspinatus tendon, between the head of the humerous and acromion during abduction/

Question 6

If a patient with active TB gets treated with isoniazid monotherapy —>

Answer 6

• rapid emergence of resistance will occur
• it occurs via two selective gene mutations, the first is decrease in bacterial expression of catalase peroxidase enzyme that is required for isoniazid activation once the drug enters the cell, and the other occur through modification of the protien target binding site for isoniazid.
• treatment of active TB is acomplished by combining multiple antibiotics to avoid selecting for resistant strains.
• however isoniazid monotherapy is used for patients with positive PPD but no evidence of clinical disease (latent Tb)

Question 7

Protein kinase A is a pathway used by

Answer 7

Increased cAMP(by adenelate cyclase) —> activates protein kinase A —> phosphorylation effect. 
-used by glucoagon, epinephrine ,...etc

Question 8

Patent foramen ovale is failure of

Answer 8

Septum primum and secondum to fuse

Can lead to paradoxical emboli (from DVT usually)

Question 9

Measles effect on vitamins

Answer 9

-VITAMIN A supplementation is recommended in acute measles. Acute measles infection depletes vitamin A stores resulting in a risk of keratitis and corneal ulceration. It helps prevent and treat these ocularcomplications in addition it reduces risk of other comorbidities, recovery time and length of hospital stay.

Question 10

Soft systolic ejection murmur at right intercostal space radiating to neck ?

Answer 10

-most likely to by aortic stenosis, usually due to bicuspid aortic valve in young asymptomatic patients.

Question 11

Features of rheumatoid arthritis

Answer 11

Clinical:
-pain, swelling and morning stiffeness in multiple joint
-small joints (PIP,MCP,MTP) and spares DIP joints
-systemic symptoms (fever,weight loss and anemia)
-cervical spine involvment, subluxation and cord compression.
LAB:
- positive RF, and anti CCP antibodies
-CRP and ESR correlate with disease activity
- x-ray:soft tissue swelling, joint space narrowing and bony erosions.

Question 12

Anticentromere antibodies are found in

Answer 12

CREST syndrome

Question 13

Acidosis effect on kidney

Answer 13

• acidosis stimulates renal ammoniagenesis, a process by which renal epethelium metabolize glutamine, generating ammonium and bicarbonate.
• ammonium ion are transported into the tubular fluid and excerted in the urine while peritubular capillaries absorb bicarbonate which functions to buffer acids in the blood.
• under normal physiologic conditions, about half of the total amount of acid secreted in the urine is in the form of ammonium and the remainder is excerted primarily as titratable acids, particulary inorganic phosphate, however increased ammonium production is almost entierly responsible for the increase in renal acid excertion seen in chronic acidosis.

Question 14

Pleotropy

Answer 14

The occurance of multiple ssmingly unrelated phenotypic manifestation often in different organ system as a result of single genetic defect.

Question 15

Direct effect of å-adrenergic agonist

Answer 15

å1 = 
-vascular smooth muscle contraction
-mydriasis
-increase urethral sphincter tone and prostate contraction
å2=
-CNS mediated decrease in BP
- decrease intraocular pressure 
-decrease lipolysis 
-decrease presynaptic NE release 
- increase platelet aggregation.

Question 16

Reflelx brady cardia

Answer 16

As a result of vasoconstriction and increase in systemic BP, baroreceptors in the carotid sinus and aortic arch causes reflex increase in vagal influence one the heart —> inhibition of pacemaker activity, slowed conduction through the AV node and decrease myocardial contractility

Question 17

Middle meningeal artery rupture =

Answer 17

Epidural hematoma, clinical presentation is charactrized by lucid interval followed by loss of consioucness. Biconvex hematoma is seen on CT

Question 18

Cortical bridging veins rupture

Answer 18

Subdural hematoma

• accumulation of blood between dura and arachnoid, they can rupture due to acceleration-deceleration injury. As hematoma expands it raises the intracranial pressure and compresses the brain.
• gradual onset of symptoms
• CT shows crescent shaped mass.

Question 19

Babesiosis

Answer 19

• acute febrile illness, thrombocytopenia, hemolytic anemia, abnormal liver function tests and intraerythrocytic inclusion (ring shaped and maltese cross forms)
• definitive diagnosis can be made from a giemsa stained thin blood smear showing intraerythrocytic parasites.
• splenectomy can increase risk of babesia

Question 20

Upper and lower motor neuron signs

Answer 20

Upper: spastic paralysis, clasp knife rigidity, hyper-reflexia and babinski sign
Lower: flaccid paralysis, hypotonia, hyporeflexia, and muscle atrophy and fasciculation.

Question 21

Combined UMN and LMN lesions are seen in

Answer 21

Amyotrophic lateral sclerosis

Question 22

Sydenham corrhea presents with

Answer 22

• Non-rhythmic movement of the hands, feet and face.

- patient’s often have sudden change in voice pitch and volume.

Question 23

Copper excretion

Answer 23

-normally excreted from the liver to the bile.

Question 24

Persistant high levels of prolactin (prolactinoma) increases risk for developing

Answer 24

Loss of bone mass

Due to E2 loss

Question 25

disopyramide

Answer 25

Class 1A antiarrythmic drug, it blocks sodium channels and inhibit initial phase 0 depolarization of action potential thereby slowing conduction. -they are responsible for phase 0 and phase 3 prolongation .

Question 26

Chlorpheniramine

Answer 26

- 1st generation antihistamine that acts by blocking both central and peripheral H1 receptors. Chlorpheniramine and other first generation antihistaminic can be very sedating because they easily penetrate the BBB and accumulate in CNS. - its contraindicated to give these medication with benzodiazepines or other sedative drugs.

Question 27

Human tumor cells resistance to chemotherapy

Answer 27

- human tumor cells developed the ability to resist chemotherapy in much the same way that many bacteria have developed resistance to antibiotics. - one of the mechanisms is via the human MDR1 gene. The prototype product of this gene is P-glycoprotein, a transembrane protein that function as an ATP dependent efflux pump. - P-glycoprotein is normally expressed in intestinal and renal tubular epithelial cells and functions to elimate foreign compounds from the body. - this protein is also present in the capillary endothelium of vessels that form the BBB. - in tumor cells, this ATP- powered transmembrane pump protein actively removes chemotheraputic agents, particulary hydrophobic agents like anthracyclines.

Question 28

IF in PSGN shows

Answer 28

Granular deposits of IgG, IgM and C3 in the GBM

Question 29

Idiopathic pulmonary fibrosis

Answer 29

Slowly progressive exertional dyspnea and dry cough , a restrictive profile on pulmonary function testing and interstitial fibrosis with cystic air space enlargement likely has IPF. - IPF shows patchy involvement with dense fibrosis and fibroblastic foci. - alveolar wall collapse leads to formation of cystic spaces (honeycombing) lined by hyperplastic type II pneumocytes or bronchiolar epithelium.

Question 30

Aspergillus flavus and aspergillus parasiticus

Answer 30

When the humidity and temperature are favorable , specific strains of the fungi aspergillus flavus and parasiticus grows on food such as corn and peanuts, producing aflatoxins as by products. - aflatoxins (B1 is most toxic) categoreized as B,A,and G. - high levels of aflatoxins —> hepatocellular carcinoma —> p53 mutation have been identified in most individuals who developedf hepatocellular carcinoma. More than 90% of these aflatoxin induced mutation are a classic G:C—>G:T transversion in codon 249.

Question 31

Gamma gltamyl transpeptidase

Answer 31

GGTP, is an enzyme predominantly present in hepatocytes and billiary epithelia. Its significant to determine wheather ALP elevation was due to liver or bone problem.

Question 32

TTP renal changes

Answer 32

Platelet rich thrombi in glomeruli and arterioles.

Question 33

Metastatic liver disease

Answer 33

CT scan usuallly shows multiple hypodense masses in the liver. - they are the most common cause of liver tumors in adults. - even with significant metastasis, patients may have no clinical or laboratory signs suggestive of hepatic insufficiency. However once the majority of the liver parenchyma is destroyed or the major bile ducts become obstructed with tumor, patients tend to present with jaundice or abnormal hepatic enzymes

Question 34

Ductus arteriosus is derived from

Answer 34

Sixth aortic arch. (On the left) | As well as pulmonary arteries(also derived from sixth aortic arch- on the right)