WBR0783
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| Author | [[PageAuthor::Serge Korjian M.D. (Reviewed by Serge Korjian)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Microbiology |
| Sub Category | SubCategory::Infectious Disease |
| Prompt | [[Prompt::A 21-year-old man presents to the emergency department for 1 week of severe sore throat with associated odynophagia. The patient also reports significant fatigue that has been keeping him in bed most of the day. The physician does a bed-side rapid strep test that returns negative. He then asks the patient to visit the lab for a simple blood test. The technologist mixes a drop of the patient’s serum with a 15% suspension of sheep red blood cells in a 5% sodium citrate solution on a glass slide. The mixture is left undisturbed for one minute after which the technologist notices that the sheep red blood cells have agglutinated. Which of the following recptors would bind the organism responsible for this patient’s disease?]] |
| Answer A | AnswerA::β2-microglobulin |
| Answer A Explanation | AnswerAExp::CMV binds β2-microglobulin. |
| Answer B | AnswerB::Sialic acid |
| Answer B Explanation | AnswerBExp::Influenza virus hemagglutinin binds to sialic acid. |
| Answer C | AnswerC::CD21 |
| Answer C Explanation | AnswerCExp::CD21 binding of EBV determines its tropism to B-cells |
| Answer D | AnswerD::Acetylcholine recptors |
| Answer D Explanation | AnswerDExp::Acetylcholine receptors are used by rabies virus to bind and enter neuronal cells. |
| Answer E | AnswerE::CD14 |
| Answer E Explanation | AnswerEExp::CD14 is a macrophage bound receptor that binds to the LPS endotoxin causing an immune reaction. |
| Right Answer | RightAnswer::C |
| Explanation | [[Explanation::Infectious mononucleosis is a clinical syndrome characterized by fever, pharyngitis, and lymphadenopathy usually caused by Ebstein-Barr virus (EBV) although several other infectious etiologies can give a mononucleosis-like syndrome including toxoplasma, and cytomegalovirus (CMV). The diagnosis is usually clinical supported by serologies and by peripheral smear showing atypical lymphocytes. Another test used to detect EBV mononucleosis vs. other mononucleosis-like syndromes is the heterophile antibody test. The test checks for agglutination of horse (Monospot test) or sheep (Paul-Bunnell test) red blood cells when mixed with the patient's serum containing the heterophile antibodies produced by EBV infected plasma cells. EBV binds to CD21 on the surface of B-cells allowing them to fuse and enter. EBV mononucleosis can be easily mistaken for streptococcal pharyngitis, and streptococcal testing is often indicated. Educational Objective: EBV causes mononucleosis by binding CD21 on the surface of B-cells. EBV infectious mononucleosis can be detected via heterophile antibody testing. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::EBV, WBRKeyword::Mononucleosis, WBRKeyword::Monospot, WBRKeyword::CD21, WBRKeyword::Pharyngitis, WBRKeyword::Heterophile antibody |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |