Practice question answers HIV infection

Practice question answers

HIV infection

© Jun Wang, MD, PhD

 

1. A. This patient presents with flu-like symptoms and diarrhea. While these presentations are not specific, the history of sexual activity with multiple partners should indicate the need of HIV screening. The recommended initial screening test for HIV is a combined immunoassay for HIV p24 and HIV antibodies. HIV-1/2 antibody test is performed after positive reaction in the initial screening test of p24 and HIV antibodies, for confirmation. HIV RNA test is usually performed when initial screening test is negative, but early HIV infection is strongly suspected, due to window period of HIV infection. Monospot test is commonly used for diagnosis of infectious mononucleosis. Rapid plasma reagin test is a screening test for primary and secondary syphilis.

 

2. C. See discussion of question 1.

 

3. A. Early HIV infection refer to the first few months, usually 6 months of HIV infection. Patient in this phase might be asymptomatic, or present with flu-like symptoms, diarrhea, etc.. Characteristic blood findings in this period usually include declining of CD4+ cells, elevated CD8+ cells, elevating HIV viral load. P24 and HIV antibodies may be positive in the later part of this phase, after the peak of viral RNA load. This patient is positive for HIV RNA, but negative for p24 and HIV antibodies, consistent with early phase of HIV infection. Acquired immunodeficiency syndrome is defined by a HIV positive patient with either a CD4+ cells less than 200/mcl, or presence of AIDS-defining conditions. AIDS usually develops years after initial HIV infection. This patient is HIV+ with symptoms, so it is not asymptomatic HIV infection. Chronic phase of HIV infection is usually asymptomatic with very low viral load, but HIV antibody will be positive.

 

4. A. HIV bind CD4 on cell surface through viral p120, followed by fusion with CCR-5, and then viral RNA enters host cells through penetrating of cell membranes by p41. HIV does not bind to CD8, CD19 or CD56. GI tract epithelial cells do not express CD4.

 

5. E. See discussion of question 4. P7 and p9 are present on nucleocapsids, and p24 is seen on capsid, not on the surface of HIV. P41 is a transmembrane protein anchoring p120 to viral envelop.

 

6. C. Binding of HIV will result in increased death in CD4+ cells, either through viral toxicity, or virus-caused inflammation. So CD4+ T cells will decline after HIV infection. Elevated lymphoblasts may be seen in acute lymphocytic leukemia. B cells and platelets are usually reduced after HIV infection. However, CD8+ T cells tend to be elevated after HIV infection.

 

7. E. HIV is usually transmitted through blood or sexual activities. Alcohol, cigarette and marijuana usage are not risk factors for HIV transmission. Hyperglycemia is commonly seen in diabetes, but not associated with generalized lymphadenopathy and other flu-like presentations as seen in this patient. Street food might be associated with diarrhea associated with infectious gastroenteritis, but not HIV infection.

 

8. D. This patient has presentations and laboratory test results of early HIV infection. HIV is usually transmitted through sexual activities or blood, including intravenous drug usages. However, the risk for blood transfusion caused HIV is very low in America, due to very comprehensive donor blood testing. This patient does not have risky sexual activities. Also see discussion of question 7.

 

9. C. Lymphoid hyperplasia is commonly seen in enlarged lymph nodes during early HIV infection. Aggregates of neutrophils in lymph nodes are seen in acute lymphadenitis. Fibrotic bands and binucleated lymphocytes are seen in nodular sclerotic Hodgkin lymphoma. Localized growth of monotonous small lymphocytes can be seen in small lymphocytic lymphoma. Sheets of atypical large B cells can be seen in diffuse large B cell lymphoma.

 

10. A. See discussion of question 3. Delayed hemolytic transfusion reaction has evidence of hemolysis, including scattered spherocytes and elevated bilirubin.

 

11. A. This is an HIV positive patient, asymptomatic except scattered lymphadenopathy. This is consistent with chronic phase of HIV infection. CD4+ T cells continue decline during this phase, even with ART. Other conditions might, but do not universally present.

 

12. B. p24 antibody usually appear since late phase of early HIV infection, and maintains a stable level in chronic phase of HIV infection until before the phase of AIDS. CD4/CD8 ratio is usually suppressed after HIV infection. P24 may disappear in chronic phase of HIV infection until before the phase of AIDS. Viral RNA load tend to be stable in chronic phase of HIV infection until before the phase of AIDS. This patient has an almost normal level of CD4+ lymphocytes that is characteristic for early to mid chronic phase.  

 

13. D. See discussion of question 3.

 

14. E. Once HIV RNA enters host cells, proviral DNA will be formed by reverse transcriptase. The proviral DNA will then be integrated into host genome by integrase. Protease will cleave Gag-pol polyprotein precursors, helping formation of new HIV core structures after proviral DNA was transcribed to viral RNA. Also see discussion of question 5.

 

15. B. See discussion of question 3.

 

16. B. See discussion of question 3.

 

17. D. This is case of lung infection with evidence of fungal yeast pneumocystis jirovecii by silver stain. Cryptococcus neoformans commonly cause skin papules and meningitis, and are characterized by yeast with thick capsules. Cytomegalovirus may infect various sites, and is characterized by large cells with large intranuclear inclusions or coarse cytoplasmic granules. Mycobacterium avium complex infection is characterized by aggregates of foamy histiocytes and densely packed acid fast bacilli visible by special stains. Toxoplasma gondii commonly cause encephalitis that is characterized by neurological manifestations and multiple ring-enhance brain lesions per MRI.

 

18. B. Toxoplasma gondii commonly cause encephalitis that is characterized by neurological manifestations and multiple ring-enhance brain lesions per MRI. Primary CNS lymphoma may have ring-enhanced brain lesions, but usually is solitary and centered in periventricular white matter. Progressive multifocal leukoencephalopathy (PML) is caused by JC virus. Cytomegalovirus (CMV) encephalitis may have periventricular enhancement. Cryptococcus neoformans may cause meningitis. However, these three do not have ring-enhanced brain lesions per MRI. Also see discussion of question 17.

 

19. C. This case is characterized by fever and neurological presentations in a HIV positive patient. The concurrent presentation of cutaneious papules with central depression, mimicking those seen molluscum contagiosum, is highly consistent with cryptococcus neoformans infection, that is confirmed with CSF findings of thick capsuled yeasts. Bartonella species are associated with bacillary angiomatosis of skin. Candida albicans infections tend to have fungal hyphae within infection tissue. Cryptosporidium usually cause diarrhea by infecting GI tract, but not meningitis. Cytomegalovirus may infect various sites, and is characterized by large cells with large intranuclear inclusions or coarse cytoplasmic granules.

 

20. B. This case is characterized by pneumonia of a HIV positive patient with biopsy findings of large cells with large intranuclear inclusions or coarse cytoplasmic granules. These findings are consistent with Cytomegalovirus infections. These giant intranuclear inclusions are not seen in other infections. Epstein-Barr virus infections might be associated with various lymphomas, including Hodgkin lymphoma. Herpes virus infections are characterized by neutrophilic infiltrate and large cells with multinucleation, nuclear molding and chromatin margining. Candida albicans infections tend to have fungal hyphae within infection tissue. Pneumocystis jirovecii pneumonia is characterized by foamy intra-alveolar exudates. The fungal yeasts of PCP can be highlighted by silver stains. Both fungi do not have thick capsules.

 

21. B. This case is characterized by visual impairment in a HIV positive patient. Fundoscopic exam reveals large area of whitening with focal intraretinal hemorrhage, a “cottage cheese with ketchup" appearance. These features are typical for CMV retinitis and diagnosis can be made by retinal findings with clinical setting of HIV infection. Cryptosporidium usually cause diarrhea by infecting GI tract. Human herpes virus 8 is commonly seen various HIV associated neoplasms, including Kaposi sarcoma and primary effusion lymphoma.  JC polyoma virus is associated with progressive multifocal leukoencephalopathy, characterized by rapidly progressive focal neurologic deficits: hemiparesis, ataxia, vision loss, aphasia. Toxoplasma gondii commonly cause encephalitis that is characterized by neurological manifestations and multiple ring-enhance brain lesions per MRI.

 

22. A. This case is characterized by progressive cognitive impairment in a HIV positive patient with less than 200/mcl CD4+ T cells. MRI reveals cortical and subcortical atrophy. These findings are consistent with HIV-associated neurocognitive disorder. JC polyoma virus is associated with progressive multifocal leukoencephalopathy, characterized by rapidly progressive focal neurologic deficits: hemiparesis, ataxia, vision loss, aphasia. Its MRI may show asymmetric demyelinating, non-enhancing white matter lesions. Alzheimer disease typically affects older patients (>65), and usually presents with gradual episodic memory loss early on, followed by language and executive dysfunction. Its MRI findings may include hippocampal atrophy, not diffuse atrophy. CMV encephalitis may have periventricular enhancement. Also see discussion of question 19.

 

23. B. This case is characterized by bilateral symmetric sensory loss, abnormal sensation, and reduced reflex in a HIV positive patient with low CD4+ count. These features are consistent with HIV-associated distal symmetric polyneuropathy. Guillain-Barré syndrome is characterized by rapid ascending weakness, areflexia, and sometimes respiratory failure. Sensation abnormality is not commonly seen in Guillain-Barre syndrome. Tabes dorsalis is a late complication of tertiary syphilis, characterized by loss of vibration, proprioception, and ataxia, due to injury of dorsal columns. Vitamin B12 deficiency may cause abnormal sensation and megaloblastic anemia. It is less likely in a patient with normal CBC. Also see discussion of question 22.

 

24. C. This case is characterized by nephrotic range proteinuria in a patient with AIDS. Sonography reveals normal sized kidneys. This is most likely HIV-associated nephropathy. Diabetic nephropathy is usually seen in patients with long-standing diabetes. This patient has normal A1c, he is unlikely diabetic, especially when no history of diabetes can be found. Hypertensive nephrosclerosis is characterized by mild proteinuria in a patient with long-standing uncontrolled hypertension. This patient has nephrotic-range proteinuria and normal blood pressure. Membranous nephropathy usually has positive ANA or anti-dsDNA. IgA nephropathy is characterized by hematuria, not nephrotic-range proteinuria.

 

 

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