A 21-year-old man is brought to the emergency department in a stuporous condition. He returned from a family visit to Mexico 2 weeks ago. One week ago, the patient began developing high-grade fever, headaches, severe myalgias, and joint pains. He had similar symptoms following a trip to Mexico 5 years ago, but at that time the symptoms did not progress and instead resolved spontaneously within a few days. Temperature is 38.3 C (101 F), blood pressure is 80/50 mm Hg, and pulse is 128/min. Examination shows a diffuse maculopapular rash, multiple purpuric lesions, and hepatomegaly. Laboratory studies show marked thrombocytopenia, leukopenia, and elevated liver aminotransferases. Which of the following is the most likely mechanism for this patient's current severe illness?

Question

A 21-year-old man is brought to the emergency department in a stuporous condition.  He returned from a family visit to Mexico 2 weeks ago.  One week ago, the patient began developing high-grade fever, headaches, severe myalgias, and joint pains.  He had similar symptoms following a trip to Mexico 5 years ago, but at that time the symptoms did not progress and instead resolved spontaneously within a few days.  Temperature is 38.3 C (101 F), blood pressure is 80/50 mm Hg, and pulse is 128/min.  Examination shows a diffuse maculopapular rash, multiple purpuric lesions, and hepatomegaly.  Laboratory studies show marked thrombocytopenia, leukopenia, and elevated liver aminotransferases.  Which of the following is the most likely mechanism for this patient's current severe illness?

Quizplus · Accepted Answer

11ec160b_381f_c44d_9249_4f00f4168253_MD0001_00 This patient's presentation after recent travel to an endemic area suggests dengue hemorrhagic fever (DHF). Dengue viruses are transmitted by the Aedes mosquito and are single-stranded RNA viruses (genus Flavivirus) with 4 different serotypes (DENV1-4). Primary (first) infection can be asymptomatic or cause a self-limited disease in most adults. Symptomatic disease can cause high-grade fever, headache, retro-orbital pain, bleeding (eg, epistaxis, petechiae/purpura), diffuse macular rash, muscle and joint pain ("break-bone fever"), leukopenia, thrombocytopenia, and elevated liver enzymes. Primary infection leads to lifelong immunity against the same serotype, but individuals can be infected with a different serotype. Secondary infection with a different viral serotype can cause a more severe illness, possibly due to antibody-dependent enhancement of infection, enhanced immune complex formation, and/or accelerated (not blunted) T-lymphocyte responses (Choice B). DHF, which can be a serious manifestation of secondary infection, is due to increased capillary permeability and can be manifested by marked thrombocytopenia, prolonged fever, respiratory/circulatory failure, and shock. Patients also develop more significant hemorrhagic tendencies (eg, petechiae with tourniquet application) and spontaneous bleeding. (Choice A) Antigenic drift refers to minor changes in viral structure that can increase the infectivity rate and lead to localized outbreaks. Antigenic drift is common annually with the influenza virus but is not typically associated with the dengue virus. (Choice D) The severity of secondary infection with dengue is usually independent of the dose of viral inoculation. (Choice E) Viral superinfection can occur with hepatitis viruses such as hepatitis D, which usually co-infects with hepatitis B. However, secondary infection with dengue is due to a different viral serotype rather than superinfection. Educational objective: Dengue viruses are single-stranded RNA viruses with 4 different serotypes. Primary (first) infection can be asymptomatic or cause a self-limited disease in most adults. Secondary infection is due to infection with a different viral serotype and usually causes more severe illness. __________ References: The pathology of dengue hemorrhagic fever. (http://www.ncbi.nlm.nih.gov/pubmed/18085063)

A 21-Year-Old Man Is Brought to the Emergency Department in a Stuporous