A 25-year-old graduate student in Boston presents - resi_hopeful

[ArchivalUser]

A 25-year-old graduate student in Boston presents to the emergency department complaining of fever, nausea, and vomiting of 6 days' duration. About 2 weeks ago, he returned from a 1-month trip to Cameroon. He felt well until 4 days ago, when he noted the onset of fevers intermittently to 38.9°C (102°F) along with shaking chills. He also had nausea with occasional bouts of emesis and a mild headache. His medical history is significant only for splenectomy at age 15 years after trauma incurred during a car accident. He takes no regular medications, although he does report taking "malaria pills" while in Africa. Since his return he has spent time with his family in Cape Cod and has taken hiking trips with his brother in the surrounding area. His temperature is 39°C (102.2°F), pulse is 120/min and regular, blood pressure is 100/60 mm Hg, respiratory rate is 26/min, and oxygen saturation is 93% on room air. His sclerae are icteric. Lung examination reveals crackles in the lower one third of the lungs bilaterally. The abdomen is soft, and the liver is palpable 4 cm below the costal margin. Skin examination reveals a round, 6-cm erythematous lesion with central clearing in the right inguinal area. Laboratory tests show:

WBC count: 7900/mm³
Hematocrit: 32%
Platelet count: 540,000/mm³
HCO3-: 15 mEq/L
Creatinine: 2.7 mg/dL
Total bilirubin: 4.3 mg/dL
Alanine aminotransferase: 15 U/L
Aspartate aminotransferase: 15 U/L
Lactate: 5.9 mmol/L

Which diagnostic test is most likely to explain the patient's clinical decompensation?

A.Serologic examination for ehrlichiosis
B.Serologic examination for Lyme disease
C.Thick peripheral blood smear
D.Thin peripheral blood smear
E.X-ray of the chest

[ArchivalUser]

I believe the answer is one of the peripheral smears bc he is has lactic acidosis from hypoxia and intravascular hemolysis.

[ArchivalUser]

A.

[ArchivalUser]

dr nish u are close... but reasoning is not close.

[ArchivalUser]

C. Morulae in WBCs

[ArchivalUser]

The correct answer is D. 39% chose this.
This patient could be infected with Plasmodium or with Babesia given his presentation and his recent exposures, and a thin peripheral blood smear would facilitate diagnosis. Babesiosis can present similarly to malaria and, in older or splenectomized patients, can be rapidly fatal. The diagnostic findings on Wright- or Giemsa-stained peripheral blood smears are intraerythrocytic ring forms. Classic, but infrequent, findings are tetrads of merozoites forming Maltese crosses. Levels of parasitemia can be 1%-80% and can be particularly high in splenectomized patients. The parasite is transmitted by the Ixodes tick, and 50% of patients will have coinfection with Borrelia burgdorferi, suggested by the erythema migrans lesion in this patient. For babesiosis, a thin smear is usually required for diagnosis because the small size of the parasites precludes a definitive diagnosis from thick smear.
A is not correct. 14% chose this.
Ehrlichiosis is a tick-borne disease caused by gram-negative, intracytoplasmic bacteria. Ehrlichia chaffeensis causes human monocytic ehrlichiosis, Anaplasma phagocytophilum causes human granulocytic anaplasmosis, and Ehrlichia ewingii is the cause of human granulocytic ehrlichiosis. Typical clinical findings include fever, myalgias, headache, and rash (macular, maculopapular, or petechial), as well as possible neurologic findings such as neck stiffness and mental status changes. Laboratory findings include leukopenia, often accompanied by thrombocytopenia and elevated transaminase levels.
B is not correct. 30% chose this.
The patient reports recent time spent in an area endemic for Lyme disease, and the rash on the patient's right groin is consistent with erythema migrans, a manifestation of acute Lyme disease. Blood work might reveal IgM antibodies. However, an infection with B. burgdorferi does not explain the patient's acute decompensation, as Lyme disease tends to be a more subacute disease with dermatologic, neurologic, and rheumatologic components. IgM will often be negative in the most acute presentations of Lyme disease, as antibodies typically take 1-2 weeks to appear.
C is not correct. 14% chose this.
A thick peripheral blood smear would be a good diagnostic modality for malaria. On thick smears, plasmodial trophozoites, schizonts, and gametocytes are seen; however, gametocytes are never intracellular. The thick smear is more sensitive in diagnosing malaria than the thin smear. The thin smear, however, allows examination of the morphologic features of both the parasites and the host RBCs, which is helpful for species identification. The thin smear also allows quantification of the parasitemia, which has prognostic and therapeutic implications.
E is not correct. 3% chose this.
A bacterial infection, especially with an encapsulated organism such as Streptococcus pneumoniae or Haemophilus influenzae, should be considered in a splenectomized patient who is acutely decompensating. However, the lack of focal findings on chest examination, as well as the absence of a significantly elevated WBC count, makes bacterial pneumonia less likely.
Bottom Line:
Malaria and babesiosis can cause clinically indistinguishable presentations. A thin peripheral blood smear allows examination of the morphologic features of both the parasites and the host RBCs, which is helpful for species identification. The thin smear also allows quantification of the parasitemia, which has prognostic significance. In splenectomized patients, treatment needs to be instituted rapidly with intravenous clindamycin and oral quinine or intravenous atovaquone and intravenous azithromycin.

[ArchivalUser]

Coinfection with Lyme and babesisa goljan clearly states this in the heme/onco chapter