UWORLD Review

Question 1

What is a Pilocytic Astrocytoma?

Answer 1

It is a cystic tumor that arises in the cerebellum, brainstem, hypothalamic region or optic pathways in children (usually posterior fossa) with a good prognosis.

Question 2

What are the microscopic or histologic features of a Pilocytic Astrocytoma?

Answer 2

Microscopic: Comprised of hairlike glial processes associated with micro cysts
Histologic: Rosenthal fibers and granular eosinophilic bodies.

Question 3

What are the symptoms of a Pilocytic Astrocytoma?

Answer 3

Nausea, vomiting, generalized headaches, ataxia and visual complaints.

Question 4

What is Glanzmann Thrombasthenia?

Answer 4

Autosomal recessive disorder caused by deficient or defective glycoprotein IIb/IIIa on platelet surfaces. Causes defect in platelet to platelet aggregation and platelet plug formation. Typically presents in childhood with mucocutaneous bleeding.

Question 5

How do you diagnose Glanzmann Thrombasthenia?

Answer 5

Peripheral smere shows no platelet clumping

Question 6

What is the mechanism of action of Abciximab? What is it used for?

Answer 6

It is a GP IIb/IIIa receptor antagonist that inhibits binding of this receptor to fibrinogen thereby preventing platelet aggregation.
It is useful in unstable angina, acute coronary syndrome and particularly in patients undergoing percutaneous coronary intervention.

Question 7

What is Paroxysmal Supraventricular Tachycardia (PSVT)?

Answer 7

An arrhythmia that arises from atrial or av nodal tissue. It is usually narrow complex with a regular and rapid rhythm. Can present as sudden onset palpitations even in healthy individuals.Can be dependent on a reentrant circuit.

Question 8

What is the treatment for PSVT?

Answer 8

Adenosine

Question 9

What and when is base excision repair used for?

Answer 9

For repairing various non-bulky DNA base alterations including depurination, alkylation, oxidation and deamination.

Question 10

What is the process of base excision repair?

Answer 10

1. Glycosylase cleaves altered DNA base from parent DNA leaving an empty sugar-phosphate site called an apurinic/apyrimidinic (AP) site.
2. Endonuclease cleaves 5’ end of AP site
3. Lyase enzyme subsequently extracts AP site from DNA molecule removing the remaining 3’ sugar-phosphate group.
4. DNA polymerase fills the gap with the correct sugar-phosphate base.
5. Ligase seals the final nick

Question 11

What is the karyotype for Turner Syndrome?

Answer 11

45, X

Patients lack an X chromosome

Question 12

What are the features of Turner Syndrome?

Answer 12

• Short stature
• Narrow high arched palate
• Low hairline
• Webbed neck
• Broad chest with widely spaced nipples
• Cubitus valgus
• Streak ovaries, amenorrhea and infertility
• Horseshoe kidney
• Bicuspid aortic valve
• Coarctation of the aorta

Question 13

What are the sexual characteristics of Turner Syndrome?

Answer 13

• Patients have normal ovarian development during fetal life.
• Due to loss of an X chromosome, by age 2 there is loss of ovarian follicles.
• Patients will have normal pubic hair, but no breast or menses due to ovarian failure

Question 14

What will the labs show for premature ovarian failure?

Answer 14

Elevated FSH and LH

Question 15

What is vaginal adenosis, what is the cause and what can it result in?

Answer 15

• It is replacement of the vaginal squamous epithelium with glandular columnar epithelium.
• Occurs in female children whose mother was exposed to diethylstilbestrol (DES) during pregnancy.
• It is a precursor to clear cell adenocarcinoma of the vagina

Question 16

What causes acute rheumatic fever?

Answer 16

Occurs 2-4 weeks after group A streptococcal pharyngitis infection.
- Antibodies produced in response to streptococcal antigens cross react with host antigens in cardiac and neuronal tissues.

Question 17

What are the complication of acute rheumatic fever?

Answer 17

Acute
- Migratory arthritis
- Pancarditis (mitral regurgitation)
- Sydenham Chorea
Chronic
- Mitral stenosis
- Valve thickens, fibroses and calcifies requiring eventual surgery.

Question 18

What is the treatment for streptococcal pharyngitis?

Answer 18

Empiric treatment with penicillin

Question 19

What is infective mononucleosis?

Answer 19

• Infection usually caused by EBV in immunocompromised patients

Question 20

What are the key features of EBV mononucleosis?

Answer 20

• Fever, hepatosplenomegaly, pharyngitis and lymphadenopathy (usually posterior cervical nodes)
• Monospot test is positive
• Spread via respiratory secretions and saliva
• Also known as the kissing disease
• Associated with lymphomas, nasopharyngeal carcinoma and lymphoproliferative disease in transplant patients.

Question 21

What are the key features of CMV infection?

Answer 21

• Mononucleosis like syndrome
• Fever, fatigue, splenomegaly, atypical lymphocytosis
• Lacks sore throat and lymphadenopathy
• Monospot test is negative in immunocompetent patients
• Can be acquired during transfusion of leukocyte-laden blood products
• Virus infects leukocytes of granulocyte-macrophage lineage

Question 22

What is the monospot test?

Answer 22

• Detects heterophiles antibodies by agglutination of horse RBCs
• Same test but with sheep blood is Paul-Bunnell test

Question 23

What are symptoms of acute decompensated heart failure?

Answer 23

Dyspnea, worsening shortness of breath with exertion, paroxysmal nocturnal dyspnea, lung sounds on auscultation, jugular venous dissension and lower extremity pitting edema

Question 24

Describe the pathogenesis of congestive heart failure.

Answer 24

1. Previous myocardial infarction leads to deleterious cardiac remodeling
2. Decreased cardiac output
3. Leads to long term neurohormonal activation
   - Sympathetic nervous system activation
   - Renin -angiotensin system activation
   - Antidiuretic hormone secretion
4. Leads to increased hemodynamic stress
   - Increased HR and contractility
   - Vasoconstriction
   - Increased extracellular volume
5. Blood pressure is maintained

Question 25

In heart failure, what happens to ventricular-endsystolic and end-diastolic pressures?

Answer 25

They are increased due to impairment of the hearts pumping ability.

Question 26

When is Brain Natriuretic Peptide released and what does it do?

Answer 26

Released by the ventricles in response to stretch (volume overload).
Causes vasodilation, diuresis/natriuresis and decreased blood pressure alleviating symptoms of heart failure.

Question 27

What is Neuroleptic Malignant Syndrome?

Answer 27

A life-threatening adverse reaction to anti-psychotic (neuroleptic) medications.
Blocks dopamine receptors in the brain leading to muscular rigidity, high fever, autonomic instability (hypertension and tachycardia) and altered sensorium.

Question 28

What is a complication of Neuroleptic Malignant Syndrome and what will labs show?

Answer 28

May result in Rhabdomyolysis and labs may show elevated creatine kinase.
May progress myoglobinuria and acute renal failure

Question 29

How do you treat Neuroleptic Malignant Syndrome?

Answer 29

Discontinue causative neuroleptic drug, supportive care and dantrolene.
Bromocriptine can also be used.

Question 30

What is the mechanism of action of Dantrolene and what is it used for?

Answer 30

It antagonizes ryanodine receptors, inhibiting calcium ion release from the sarcoplasmic reticulum of skeletal muscle thereby reducing muscle rigidity and contraction.