Day #44 - HIV

Today's case was a patient with HIV who presented with fever, confusion, headache, anorexia and malaise. His CD4 count was less than 100.

We discussed, based on the clinical features that the patient probably had a CNS infection of a indolent nature. The differential included toxoplasmosis, cryptococcosis, TB meningitis, syphilis, viral encephalitis or non-infectious causes like primary CNS lymphoma. The normal CT scan left cryptococcosus, TB meningitis, syphilis or viral encephalitis. The CSF studies confirmed cryptococcal meningitis, of which this was a fairly classic case.

The IDSA has guidelines for the management of cryptococcal meningitis, and this RCT in NEJM is probably the landmark study.

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Remember in HIV there is a marked increase in the risk of certain infections:

• Any CD4 count: TB, pneumococcus, herpes simplex, varicella zoster
  
• CD4 less than 200 Pneumocystis Carini
• CD4 less than 100 Toxoplasmosis, Cryptococcus
  
• CD4 less than 50: CMV, Mycobacterium Avium Complex
  

We also talked about HIV treatment using the viral life cycle as a guide. In general, we initiate treatment if:

• The patient is ready to take the medication
• AIDS defining event OR
• CD4 >350 with rapidly decreasing CD4 and very high viral load
• CD4 less than 350 stongly consider starting
  
• CD4 less than 200 start
  

Using the viral life cycle, we talked about the various medications that are available:

• Viral fusion inhibitors (T20)
• Chemokine inhibitors CCR5 (miraviroc)
• Reverse transcriptase inhibitors (NRTI -- eg tenofovir, ermtrictabine/lamivudine, abacavir) and (NNRTI -- effavirenz)
• Protease inhibitors (lopinavir/ritonavir, atazanavir/ritonavir)
• Integrase inhibitors (raltegravir)

General rule: 2NRTI + PI or NNRTI in treatment naive, in experienced patients who are failing goal is to develop regimen which has 3 active drugs in multiple classes.

We discussed the "AIDS" defining criteria (CD4 less than 200 or specific conditions - see list). Guidelines for the management of HIV and opportunistic infections are available here.