USMLE Forum Archives - USMLE Step 2 CK - IM 44
IM 44
TheOne - 06-11-07 19:26
A 19 years old African American woman with sickle-cell disease is brought to the physician because she is "more pale than usual," lethargic, and having some respiratory problems. About 6 days before the visit she developed a low grade fever of 38.5 C (103.6 F) with complaints of generalized body aches, loss of appetite, and lethargy. Her mother also noticed development of a rash that has since disappeared. The young woman denies any substance use and has not been sexually active. The patient's vital signs are: temperature 38.9 C (104.3 F), pulse 110/min, blood pressure 110/50 mm Hg, respirations 24/min, and oxygen saturation 96%. Physical examination shows a woman with mildly labored breathing with pale mucous membranes, cool extremities, and delayed capillary refill. There is no evidence of any localized tenderness on examination. The rest of her physical examination is unremarkable. Laboratory studies show:
WBC count 9000/mm3
Hemoglobin 4.5g/dL
Hematocrit 13%
Platelets 160,000/mm3
Reticulocyte count 0.01%
A peripheral blood smear shows no evidence of any erythroid precursors. Which of the following is the most likely pathogen?
A. Chlamydia
B. Coronavirus
C. Neisseria
D. Parvovirus
E. Streptococcus
TheOne - 06-11-07 19:26
A 19 years old African American woman with sickle-cell disease is brought to the physician because she is "more pale than usual," lethargic, and having some respiratory problems. About 6 days before the visit she developed a low grade fever of 38.5 C (103.6 F) with complaints of generalized body aches, loss of appetite, and lethargy. Her mother also noticed development of a rash that has since disappeared. The young woman denies any substance use and has not been sexually active. The patient's vital signs are: temperature 38.9 C (104.3 F), pulse 110/min, blood pressure 110/50 mm Hg, respirations 24/min, and oxygen saturation 96%. Physical examination shows a woman with mildly labored breathing with pale mucous membranes, cool extremities, and delayed capillary refill. There is no evidence of any localized tenderness on examination. The rest of her physical examination is unremarkable. Laboratory studies show:
WBC count 9000/mm3
Hemoglobin 4.5g/dL
Hematocrit 13%
Platelets 160,000/mm3
Reticulocyte count 0.01%
A peripheral blood smear shows no evidence of any erythroid precursors. Which of the following is the most likely pathogen?
A. Chlamydia
B. Coronavirus
C. Neisseria
D. Parvovirus
E. Streptococcus
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#1
Re: IM 44 Sarahhh - 06-12-07 00:54 Parvovirus B19 causes aplastic crisis.. affects the bone marrow and lowers the Hct as well.. D
#2
Re: IM 44 jwang - 06-13-07 12:04 I believe the answer is D (parvo B19) because it causes severe hemolytic anemia is cases of sickle cell (which I believe our woman has)
#3
Re: IM 44
TheOne - 06-19-07 15:16 The correct answer is D. This patient is presenting with aplastic crisis, a potentially fatal complication seen in sickle-cell patients. The purported organism in over 70% of cases is parvovirus B19, a virus implicated in erythema infectiosum ("fifth disease"). The virus causes a transient red cell aplasia; bone marrow often shows lack of erythroid precursors. Sickle-cell patients who already have decreased number of red blood cells that tend to have shorter life span (on the order of 10 days) can be severely affected by this aplastic crisis. Red blood cell transfusions are lifesaving in this patient population.
#5
Re: IM 44 babbu5508 - 07-07-10 00:24 D. Parvovirus can cause a temporary infection of the bone marrow cells, shutting down production of red blood cells for about 10 days. In most people, this temporary marrow shutdown is not a problem. However, since people with sickle cell disease (or other blood problems such as hereditary spherocytosis or thalassemia) depend on brisk production of red blood cells to replace their rapidly destroyed sickled cells, even temporary marrow shutdown can cause severe worsening of anemia for about two weeks
#6
Re: IM 44 bingousmle - 07-12-10 05:42 aplastic crisis a complication seen in sickle-cell patients due to parvovirus B19 infection since Hemoglobin 4.5g/dL, Hematocrit 13% and Reticulocyte count 0.01%
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