L28 Lymphadenopathy and HIV infection Flashcards
What are the 4 causes of Lymphadenopathy
- Proliferation of lymphocytes in response to a local infection
- Proliferation of malignant cells that have metastasised to the node by lymphatic spread
- Proliferation of malignant lymphocytes (diffuse chronic/acute lymphoma)
- Inflammation within nodes resulting from killing of lymphocytes infected by a virus (diffuse)
How is lymphadenopathy investigated
- Look for adjacent infection (boils/cellulitis)
- Look for adjacent cancer -breast, lung, skin
- Look for features of cells in lymph node - skin biopsy, fine needle aspiration to determine if malignant cells present
- Look for evidence of an infection that targets lymphoid cells
What are the potential viral and bacterial agents which cause Infections of lymph nodes
Bacterial:
- Staph aureus (mainly tropical countries)
- Mycobacterium Tuberculosis (10% which don’t get pneumonia)
Viral:
- Epstein Barr Virus (common)
- Cytomegalovirus (less severe)
- HIV
What are different Herpes viruses and their characteristics
- EBV, CMV
- Herpes simplex: cold sores
- Varicella Zoster virus: chicken pox, shingles
Herpes viruses are DNA viruses that begin with acute infection followed by
- latent infection (asymptomatic) with reactivation leading to
- chronic infection (asymptomatic) or recurrent infection.
How does Acute EBV (glandular fever) present, ages, transmission and time course of disease
As a child quite minor, adult/adolescent more severe illness. >90% had EBV ~20yrs
Virus transmitted in saliva and after recovery there is persistent salivary excretion of EBV
- Incubated for 4-6 wks
- Illness for 1-2 wks - needs rest and paracetamol
Fever, sore throat, cervical adenopathy, malaise, fatigue
How is EBV infection diagnosed with lab tests compared to acute CMV
Both have
1. Lymphocytosis (>50% of WBCs)
- Atypical lymphocytes (bigger size and nucleus)
- Abnormal Liver FT
EBV has
4. Monospot test which detects heterophile antibodies for equine RBC (not EBV) produced by humans after EBV infection
- Specific EBV serology: detecting EBV antigen in blood, and antibodies that bind to specific parts of EBV
CMV has
- Detection of IgM or IgG to CMV
- Detection of CMV DNA in blood
What is the presentation of acute HIV infection and what will be the changes in the blood
With recent HIV exposure 3-6 weeks prior, will present with glandular fever like illness due to the killing off of infected lymphocytes.
Test for presence of antibodies to HIV in blood
- Will have persistent virus in blood and genital secretions
What is the time course of HIV infection (untreated and treated)
- Infection of CD4 lymphocytes
- small number of infected cells produce HIV, causing HIV levels in tissues and blood to rise
- Cytotoxic T lymphocytes kill many HIV producing cells, reducing their numbers in the blood and causing brief glandular fever like illness.
- B lymphocytes start producing antibodies to HIV
- HIV remains stable for many years while helper T lymphocyte number continues to fall
–Treatment will keep the virus conc low and allow helper lymphocyte numbers to recover
- If not then helper lymphocyte depletion is severe leading to AIDS illnesses, increased HIV in blood and death
What are the diagnoses of HIV infection - including steps
- Detect antibodies to HIV in blood
a) screening test = ELISA - HIV antigen stuck to the base of ELISA wells
- Serum sample added and antibody in serum will attach to HIV antigen
- Anti-human antibody with adherent enzyme is added and attaches to the serum antibody
- Reagent added and the cleavage by enzyme on AHA results in colour change in proportion to the amount of HIV antibody
b) confirmatory test: Western blot (old)
- HIV proteins separated depending on molecular weight and charge by gel electrophoresis
- proteins transferred from gel to membrane by western blotting
- Membrane strips incubated in patient serum, antibodies will attach to separated HIV protein bands - more bands the longer the infection so if not so many, check back in 3-4 wks
- Human antibodies are stained with silver dye.
- Detect HIV genome in blood PCR
What is AIDS and AIDS defining illnesses
Acquired immune deficiency syndrome
Defining illnesses:
- pneumocystitis jiroveci pneumonia
- toxoplasma gondii brain absesses
- Candida albicans oesophagitis
- Kaposi’s sarcoma (caused by HHV8)
How is the risk for HIV infection increased for hetero, MSM and mother-infant HIV transmission
Related to the surface area of mucosa exposed and length of time exposed to genital secretions so birth is 25% at delivery
