An 18-year-old woman is brought to the emergency department due to 3 days of fever, severe headache, nausea, and vomiting. She attends college in North Carolina and has been sexually active with a male partner. Temperature is 39.4 C (102.9 F), blood pressure is 80/55 mm Hg, and pulse is 146/min. The patient is ill-appearing and poorly arousable. The neck is supple, with no jugular venous distension, nuchal rigidity, or lymphadenopathy. Chest examination reveals bilateral rales. A diffuse maculopapular rash with numerous petechiae is seen on the trunk, extremities, hands, and feet. Lumbar puncture reveals the following: Which of the following organisms is the most likely cause of this patient's clinical presentation?

Question

An 18-year-old woman is brought to the emergency department due to 3 days of fever, severe headache, nausea, and vomiting.  She attends college in North Carolina and has been sexually active with a male partner.  Temperature is 39.4 C (102.9 F), blood pressure is 80/55 mm Hg, and pulse is 146/min.  The patient is ill-appearing and poorly arousable.  The neck is supple, with no jugular venous distension, nuchal rigidity, or lymphadenopathy.  Chest examination reveals bilateral rales.  A diffuse maculopapular rash with numerous petechiae is seen on the trunk, extremities, hands, and feet.  Lumbar puncture reveals the following:  Which of the following organisms is the most likely cause of this patient's clinical presentation?

Quizplus · Accepted Answer

11ec25c8_d46a_abb8_bc81_5b393d3120e2_MD0003_00 This patient's constitutional symptoms, confusion, signs of septic shock (eg, fever, tachycardia, hypotension), petechial rash, and minimal leukocytosis on lumbar puncture raise strong suspicion for Rocky Mountain spotted fever (RMSF), a tick-borne illness caused by Rickettsia rickettsii. This bacterium attacks vascular endothelial cells, which causes progressive capillary permeability, fluid extravasation, hypovolemia, and poor tissue perfusion. Most patients have 3-4 days of constitutional symptoms (eg, fever, myalgia, nausea, vomiting, headache) that resemble a viral illness. A maculopapular rash subsequently develops on the wrists and ankles, involves the palms/soles, and progresses centrally. Over time, increased microvascular injury causes the rash to become petechial, a classic feature of RMSF. Life-threatening noncardiogenic pulmonary edema (eg, bilateral rales) and shock (eg, hypotension, tachycardia, poor arousal) can occur. Laboratory assessment typically reveals thrombocytopenia due to intravascular platelet destruction and hyponatremia (increased ADH due to hypovolemia). Lumbar puncture can help rule out meningococcal meningitis, which also causes petechial rash, fever, and sepsis. Patients with meningococcal meningitis usually have cerebrospinal fluid evidence of dramatic leukocytosis (eg, >1000/mm³), high protein, and low glucose (Choice C), whereas those with RMSF usually have mild leukocyte elevation (eg, <100/mm³), minimal protein elevation, and normal glucose. Suspected RMSF should be urgently treated with empiric doxycycline to prevent progression and death. Supportive treatment (eg, intravenous fluids) should also be administered to those with shock. The diagnosis is confirmed with serologic testing. (Choice A) Acute HIV infection often presents with constitutional symptoms and maculopapular rash on the trunk, neck, and face, not the palms/soles. Most patients also have diffuse lymphadenopathy, sore throat, and (often) mucocutaneous ulcers. Shock would be atypical. (Choice B) Herpes encephalitis is usually marked by acute constitutional symptoms, focal neurologic deficits, and/or seizure. The herpes rash is vesicular, not maculopapular, and typically occurs around the mouth or genitals. Lumbar puncture usually reveals significant red blood cells in the cerebrospinal fluid. Educational objective: Rocky Mountain spotted fever is a tick-borne illness caused by Rickettsia rickettsii. Classic symptoms include a few days of fever and headache, followed by a maculopapular or petechial rash that may involve the palms/soles. Without empiric antibiotic treatment (eg, doxycycline), noncardiogenic pulmonary edema and shock can occur. References: The evaluation and management of Rocky Mountain spotted fever in the emergency department: a review of the literature. (http://www.ncbi.nlm.nih.gov/pubmed/29685474) Rickettsia rickettsiae (Rocky Mountain spotted fever). (http://www.ncbi.nlm.nih.gov/pubmed/28613631)

An 18-Year-Old Woman Is Brought to the Emergency Department Due