NEET PG 2018 MCQ'S - SAMS PG

1
SAMS PG MCQs
2

• The answer is A.
• Polycythemia vera (PV) is a clonal disorder that
  involves a multipotent hematopoietic progenitor
  cell. Clinically, it is characterized by a
  proliferation of red blood cells (RBCs),
  granulocytes, and platelets. The precise etiology
  is unknown. Unlike chronic myelogenous leukemia,
  no consistent cytogenetic abnormality has been
  associated with the disorder. However, a mutation
  in the autoinhibitory, pseudokinase domain of the
  tyrosine kinase JAK2that replaces valine with
  phenylalanine , causing constitutive activation
  of the kinaseappears to have a central role in
  the pathogenesis of PV. Erythropoiesis is
  regulated by the hormone erythropoietin. Hypoxia
  is the physiologic stimulus that increases the
  number of cells that produce erythropoietin.
  Erythropoietin may be elevated in patients with
  hormone-secreting tumors. Levels are usually
  normal in patients with hypoxic erythrocytosis.
  In PV, however, because erythrocytosis occurs
  independently of erythropoietin, levels of the
  hormone are usually low. Therefore, an elevated
  level is not consistent with the diagnosis. PV is
  a chronic, indolent disease with a low rate of
  transformation to acute leukemia, especially in
  the absence of treatment with radiation or
  hydroxyurea. Thrombotic complications are the
  main risk for PV and correlate with the
  erythrocytosis. Thrombocytosis, although
  sometimes prominent, does not correlate with the
  risk of thrombotic complications. Salicylates are
  useful in treating erythromelalgia but are not
  indicated in asymptomatic patients. There is no
  evidence that thrombotic risk is significantly
  lowered with their use in patients whose
  hematocrits are appropriately controlled with
  phlebotomy. Phlebotomy is the mainstay of
  treatment. Induction of a state of iron
  deficiency is critical to prevent a reexpansion
  of the RBC mass. Chemotherapeutics and other
  agents are useful in cases of symptomatic
  splenomegaly. Their use is limited by side
  effects, and there is a risk of leukemogenesis
  with hydroxyurea.

3

• The answer is B.
• Cat bites are the most likely animal bites to
  lead to cellulitis because of deep inoculation
  and the frequent presence of Pasteurella
  multicoda. In an immunocompetent host, only cat
  bites warrant empirical antibiotics. Often the
  first dose is given parenterally.
  Ampicillinsulbactam followed by oral
  amoxicillinclavulanate is effective empirical
  therapy for cat bites. However, in an asplenic
  patient, a dog bite can lead to rapid
  overwhelming sepsis as a result of Capnocytophaga
  canimorsus bacteremia. These patients should be
  followed closely and given third-generation
  cephalosporins early in the course of infection.
  Empirical therapy should also be considered for
  dog bites in elderly adults, for deep bites, and
  for bites on the hand.

4

• The answer is D.
• Although any valvular vegetation can embolize,
  vegetations located on the mitral valve and
  vegetations larger than 10 mm are greatest risk
  of embolizing. Of the answer choices, C, D, and E
  are large enough to increase the risk of
  embolization. However, only choice D demonstrates
  the risks of both size and location.
  Hematogenously seeded infection from an embolized
  vegetation may involve any organ but particularly
  affects those organs with the highest blood flow.
  They are seen in up to 50 of patients with
  endocarditis. Tricuspid lesions lead to pulmonary
  septic emboli, which are common in injection drug
  users. Mitral and aortic lesions can lead to
  embolic infections in the skin, spleen, kidneys,
  meninges, and skeletal system. A dreaded
  neurologic complication is mycotic aneurysm,
  focal dilations of arteries at points in the
  arterial wall that have been weakened by
  infection in the vasa vasorum or septic emboli,
  leading to hemorrhage.

5

• The answer is B.
• Bullae (Latin for bubbles) are skin lesions that
  are greater than 5 mm and fluid filled. They may
  be regular or irregularly shaped and filled with
  serous or seropurulent fluid. Clostridium spp.,
  including perfringens, may cause bullae through
  myonecrosis. Staphylococcus causes scalded skin
  syndrome through elaboration of the exfoliatin
  toxin from phage group II, particularly in
  neonates. Streptococcus pyogenes, the causative
  agent of impetigo, may cause bullae initially
  that progress to crusted lesions. MRSA may also
  cause impetigo. The halophilic Vibrio, including
  V. vulnificus, may cause an aggressive fasciitis
  with bullae formation. Patients with cirrhosis
  exposed to Gulf of Mexico or Atlantic waters (or
  ingestion of raw seafood from those waters) are
  at greatest risk. Infection with the dimorphic
  fungus, Sporothrix schenckii, presents with
  discrete crusted lesions resembling ringworm.
  Lesions may progress to ulcerate. Patients often
  have a history of working with soil or roses.

6

• The answer is E.
• Although frequent nonbloody diarrheal illness is
  commonly associated with Clostridium difficile
  infection, other presentations are well
  described, including fever in 28 of cases,
  abdominal pain, and leukocytosis. Adynamic ileus
  is often seen with C. difficile infection, and
  leukocytosis in this condition should be a clue
  that C. difficile is at play. Recurrent infection
  after therapy has been described in 15 to 30 of
  cases.

7

• The answer is A.
• Common causes of urethral discomfort and
  discharge in men include Chlamydia trachomatis,
  Neisseria gonorrhoeae, Mycoplasma genitalium,
  Ureaplasma urealyticum, Trichomonas vaginalis,
  and herpes simplex virus. Gardnerella spp. is the
  usual cause of bacterial vaginosis in women and
  is not a pathogen in men.

8

• The answer is E.
• Probably because of its ubiquity and ability to
  stick to foreign surfaces, Staphylococcus
  epidermidis is the most common cause of
  infections of central nervous system shunts as
  well as an important cause of infections on
  artificial heart valves and orthopedic
  prostheses. Corynebacterium spp. (diphtheroids),
  similar to S. epidermidis, colonize the skin.
  When these organisms are isolated from cultures
  of shunts, it is often difficult to be sure if
  they are the cause of disease or simply
  contaminants. Leukocytosis in cerebrospinal
  fluid, consistent isolation of the same organism,
  and the character of a patients symptoms are all
  helpful in deciding whether treatment for
  infection is indicated.

9

• The answer is D.
• Resistance to ampicillin and vancomycin is far
  more common in strains of Enterococcus faecium
  than E. faecalis. Linezolid and
  quinupristindalfopristin are approved by the
  U.S. Food and Drug Administration for the
  treatment of some vancomycin-resistant
  enterococci (VRE) infections. Linezolid is not
  bactericidal, and its use in severe endovascular
  infections has produced mixed results therefore,
  it is recommended only as an alternative to other
  agents. Quinupristindalfopristin is not active
  against most E. faecalis isolates. Resistance to
  VRE strains of E. faecium is also emerging with
  increasing usage. Cephalosporins are generally
  inactive against enterococcal infections.

10

• The answer is A.
• Neisseria meningitidis is an effective colonizer
  of the human nasopharynx, with asymptomatic
  infection rates of greater than 25 described in
  some series of adolescents and young adults and
  among residents of crowded communities. Despite
  the high rates of carriage among adolescents and
  young adults, only 10 of adults carry
  meningococci, and colonization is very rare in
  early childhood. Colonization should be
  considered the normal state of meningococcal
  infection. Meningeal pharyngitis rarely occurs.
  Meningococcal disease occurs when a virulent form
  of the organism invades a susceptible host. The
  most important bacterial virulence factor relates
  to the presence of the capsule. Unencapsulated
  forms of N. meningitides rarely cause disease. A
  nonblanching petechial or purpuric rash occurs
  in more than 80 of cases of meningococcal
  disease. Of patients with meningococcal disease,
  30 to 50 present with meningitis,
  approximately 40 with meningitis plus
  septicemia, and 20 with septicemia alone.
  Patients with complement deficiency, who are at
  highest risk of developing meningococcal disease,
  may develop chronic meningitis.

11

• The answer is B.
• The major reservoirs in the human body for
  anaerobic bacteria are the mouth, lower
  gastrointestinal tract, skin, and female genital
  tract. Generally, anaerobic infections occur
  proximal to these sites after the normal barrier
  (i.e., skin or mucous membrane) is disrupted.
  Thus, common infections resulting from these
  organisms are abdominal or lung abscess,
  periodontal infection, gynecologic infections
  such as bacterial vaginosis, and deep tissue
  infection. Properly obtained cultures in these
  circumstances generally grow a mixed population
  of anaerobes typical of the microenvironment of
  the original reservoir.

12

• The answer is E.
• Sinoatrial dysfunction is often divided into
  intrinsic disease and extrinsic disease of the
  node. This is a critical distinction, as
  extrinsic causes are often reversible and
  pacemaker placement is not required. Drug
  toxicity is a common cause of extrinsic,
  reversible sinoatrial dysfunction, with common
  culprits including beta blockers, calcium
  channel blockers, lithium toxicity, narcotics,
  pentamidine, and clonidine. Hypothyroidism, sleep
  apnea, hypoxia, hypothermia, and increased
  intracranial pressure are all reversible forms of
  extrinsic dysfunction. Radiation therapy can
  result in permanent dysfunction of the node and
  therefore is an irreversible, or intrinsic, cause
  of sinoatrial node dysfunction. In symptomatic
  patients, pacemaker insertion may be indicated.

13

• The answer is E.
• Patients at the highest risk for stroke
  associated with atrial fibrillation include those
  with a prior history of stroke, TIA, or embolism,
  and patients with hypertension, diabetes
  mellitus, congestive heart failure, rheumatic
  heart disease, LV dysfunction, and marked left
  atrial dilation of greater than 5.0 cm or age
  greater than 65 years. Anticoagulation should be
  strongly considered in these patients. Increased
  left atrial size is a risk factor for chronic
  atrial fibrillation.

14

• The answer is E.
• Atrial septal defect (ASD) is a not uncommon
  simple congenital heart disease lesion that is
  often diagnosed in adults. Because of chronic
  left-to-right shunting of intracardiac blood,
  pulmonary arterial hypertension is a
  well-recognized common complication. With the
  development of pulmonary arterial hypertension,
  the potential for paradoxical embolization of
  either air or thrombotic material from the right
  atrium to the systemic circulation is increased.
  Similarly, with exertion in the context of
  pulmonary arterial hypertension and ASD, blood
  may shunt right to left, leading to systemic
  arterial oxygen desaturation. Atrial fibrillation
  or other supraventricular arrhythmias may occur,
  also as a result of atrial stretching with the
  lesion. While atherosclerosis and unstable angina
  may certainly occur in adults, is not a reported
  complication

15

• The answer is A.
• Patients with severe aortic regurgitation will
  have a water-hammer pulse that collapses
  suddenly as arterial pressure rapidly falls
  during late systole and diastole, a so-called
  Corrigans pulse. Capillary pulsations seen in
  the nail bed in severe aortic regurgitation are
  named Quinckes pulse. Traubes sign, or a pistol
  shot sound, may be heard over the femoral
  arteries and Duroziezs sign, with a to-and-fro
  murmur over the femoral artery, have also been
  described. Pulsus parvus et tardus is found in
  severe aortic stenosis. Pulsus bigeminus occurs
  when there is a shorter interval after a normal
  beat with a following low volume pulse, often
  with a premature ventricular beat. Pulsus
  paradoxus has been described with pericardial
  tamponade or severe obstructive lung disease.
  Pulsus alternans is alternating large and small
  volume pulses seen in severe heart failure.

16

• The answer is E.
• Tricuspid regurgitation is most commonly caused
  by dilation of the tricuspid annulus due to
  right-ventricular enlargement of any cause. Any
  cause of left-ventricular failure that results in
  right-ventricular failure may lead to tricuspid
  regurgitation. Congenital heart diseases or
  pulmonary arterial hypertension leading to
  right-ventricular failure will dilate the
  tricuspid annulus. Inferior wall infarction may
  involve the right ventricle. Rheumatic heart
  disease may involve the tricuspid valve, although
  less commonly than the mitral valve. Infective
  endocarditis, particularly in IV drug users, will
  infect the tricuspid valve, causing vegetations
  and regurgitation. Other causes of tricuspid
  regurgitation include carcinoid heart disease,
  endomyocardial fibrosis, congenital defects of
  the atrioventricular canal, and right-ventricular
  pacemakers.

17

• The answer is A.
• Bioprosthetic valves are made from human,
  porcine, or bovine tissue. The major advantage of
  a bioprosthetic valve is the low incidence of
  thromboembolic phenomena, particularly 3 months
  after implantation. Although in the immediate
  postoperative period some anticoagulation may
  occur, after 3 months there is no further need
  for anticoagulation or monitoring. The downside
  is the natural history and longevity of the
  bioprosthetic valve. Bioprosthetic valves tend to
  degenerate mechanically. Approximately 50 will
  need replacement at 15 years. Therefore, these
  valves are useful in patients with
  contraindications to anticoagulation, such as
  elderly patients with comorbidities and younger
  patients who desire to become pregnant. Elderly
  people may also be spared the need for repeat
  surgery, as their life span may be shorter than
  the natural history of the bioprosthesis.
  Mechanical valves offer superior durability.
  Hemodynamic parameters are improved with
  double-disk valves compared with single-disk or
  ball-and-chain valves. However, thrombogenicity
  is high and chronic anticoagulation is
  mandatory. Younger patients with no
  contraindications to anticoagulation may be
  better served by mechanical valve replacement.

18

• The answer is E.
• Many infectious etiologies have been associated
  with the development of inflammatory myocarditis
  including viral agents (coxsackie, adenovirus,
  HIV, hepatitis C) and parasitic agents, with
  Chagas disease or T. cruzi being most prominent,
  but also toxoplasmosis. Additionally, bacterial
  etiologies like diphtheria, spirochetal disease
  like Borrelia burgdorferi, rickettsial disease,
  and fungal infections have been associated.

19

• The answer is B.
• Pulsus paradoxus is an exaggeration of the normal
  phenomenon in which systolic blood pressure
  declines 10 mmHg or less with inspiration. Pulsus
  paradoxus is typically seen in patients with
  pericardial tamponade and in patients with severe
  obstructive lung disease (COPD, asthma). In
  pulsus paradoxus due to pericardial tamponade,
  the inspiratory systolic blood pressure decline
  is greater due to the tight incompressible
  pericardial sac. The right ventricle distends
  with inspiration, compressing the left ventricle
  and resulting in decreased systolic pulse
  pressure in the systemic circulation. In severe
  obstructive lung disease, the inspiratory decline
  of systolic blood pressure may be due to the
  markedly negative pleural pressure either causing
  left ventricular compression (due to increased RV
  venous return) or increased LV impedance to
  ejection (increased afterload).

20

• The answer is C.
• Becks triad can be used to alert clinicians to
  the potential presence of cardiac tamponade. The
  principal features are hypotension, muffled or
  absent heart sounds, and elevated neck veins,
  often with prominent x-descent and absent
  y-descent. These are due to the failure of
  ventricular filling and limited cardiac output.
  Kussmauls sign is seen in restrictive
  cardiomyopathy and pericardial constriction, not
  tamponade. Friction rub may be seen in any
  condition associated with pericardial
  inflammation.

21

• The answer is B.
• The functional residual capacity of the lung
  refers to the volume of air that remains in the
  lung following a normal tidal respiration. This
  volume of air represents the point at which the
  outward recoil of the chest wall is in
  equilibrium with the inward elastic recoil of the
  lungs. The lungs would remain at this volume if
  not for the actions of the respiratory muscles.
  The functional residual capacity is comprised of
  two lung volumes the expiratory reserve volume
  and the residual volume. The expiratory reserve
  volume represents the additional volume of air
  that can be exhaled from the lungs when acted
  upon by the respiratory muscles of exhalation.
  The residual volume is the volume of air that
  remains in the lung following a complete
  exhalation and is determined by the closing
  pressure of the small airways.