RNA viruses – Part II

Asked once on an old, offline NBME. USMLE wants you to know it has a bird reservoir and is spread by Culex mosquito.

Presents as flu-like illness in most people. The NBME Q simply gives patient with headache and fever + they say the causal organism is spread by Culex mosquito and has a bird reservoir –> answer = West Nile virus.

Anemia of chronic disease

Low Hb, low iron, normal ferritin.

Some students will get pedantic and say ferritin can be high. Rarely it can be high in AoCD, yes. But the point is that it’s almost always normal.

Don’t confuse the low iron / normal ferritin combo with thalassemia, which is normal iron / normal ferritin. If the heme stuff seems difficult/elusive, go to my HY Hematology PDF.

Congenital rubella presents as patent ductus arteriosus (PDA) in a neonate. Exceedingly HY / pass-level. Cataracts and deafness also possible.

HAART therapy is initiated immediately upon diagnosis of HIV. We do not wait for CD4 count to fall to a certain level before commencing.

Once CD4 count falls below 200/μL, patients are started on trimethoprim/sulfamethoxazole (TMP/SMX) for Pneumocystis jiroveci pneumonia (PJP) prophylaxis.

NBME has Q where they give you an HIV patient with CD4 count of, e.g., 550, and then ask what type of drug regimen needs to be commenced. Answer in this case is “three drug anti-retroviral therapy alone,” where “three drug anti-retroviral therapy + Pneumocystis prophylaxis” is wrong, as well as all answers that say two-drug regimen.

Highly active anti-retroviral therapy (HAART) consists of three drugs: two nucleoside reverse-transcriptase inhibitors (NRTI) + either a non-nucleoside reverse-transcriptase inhibitor (NNRTI) or protease inhibitor.

To prevent vertical transmission, the most important measure to take is HAART therapy while pregnant + keeping the mother’s viral load as low as possible. She will then receive intrapartum zidovudine, C-section is performed, and then the neonate will receive 6 weeks of zidovudine commenced within 12 hours of birth. Some students will get pedantic about various alternative/updated regimens for neonates, but one of the NBMEs assesses this point about 6 weeks of zidovudine commenced within 12 hours of birth.

Transmitted almost exclusively from IV drugs/blood exposure. Not present in breastmilk and non-sanguineous body fluids (in contrast to HepB).

Progressive multifocal leukoencephalopathy (PML) is neuronal degeneration over weeks to months caused by reactivation of JC polyoma virus.

USMLE wants you to know this is “reactivation of latent infection.” “Acute infection in HIV patient” is wrong answer.

Cryptococcal neoformans meningitis, which presents with low glucose, high protein, and high lymphocytes. Diagnosed with CSF latex agglutination (most accurate), or India ink prep, or mucicarmine staining.

HIV

Adults with severe acute-onset seborrheic dermatitis, disseminated scabies, or molloscum contagiosum should have an HIV test.

Rubella.

Causes fever and head-to-toe maculopapular rash in unvaccinated children (and adults).

HY point about the presentation is that it causes post-auricular and sub-occipital lymphadenophathy.

Adults can get arthritis. For example, if the USMLE gives you a neonate with congenital rubella syndrome + they ask what symptom the woman most likely had when pregnant, arthritis can be an answer if rash is not listed. USMLE will not force you to choose between rash and arthritis. The point is that you merely are aware arthritis is HY in adults as part of the presentation.

Congenital rubella presents as patent ductus arteriosus (PDA) in a neonate. Exceedingly HY / pass-level. Cataracts and deafness also possible.

Spread usually by Aedes mosquito.

Causes flu-like illness and jaundice (hence yellow fever) due to hepatocellular damage. Councilman bodies are seen on biopsy of the liver, which are apoptotic bodies.

Causes fever and head-to-toe maculopapular rash in unvaccinated children (and adults).

HY point about the presentation is that it causes post-auricular and sub-occipital lymphadenophathy.

Adults can get arthritis. For example, if the USMLE gives you a neonate with congenital rubella syndrome + they ask what symptom the woman most likely had when pregnant, arthritis can be an answer if rash is not listed. USMLE will not force you to choose between rash and arthritis. The point is that you merely are aware arthritis is HY in adults as part of the presentation.

Congenital rubella presents as patent ductus arteriosus (PDA) in a neonate. Exceedingly HY / pass-level. Cataracts and deafness also possible.

Highly active anti-retroviral therapy (HAART) consists of three drugs: two nucleoside reverse-transcriptase inhibitors (NRTI) + either a non-nucleoside reverse-transcriptase inhibitor (NNRTI) or protease inhibitor.

HAART therapy is initiated immediately upon diagnosis of HIV. We do not wait for CD4 count to fall to a certain level before commencing.

HIV patients with CD4 counts under 200, or those who get any HIV-related opportunistic infection, are said to have Acquired Immunodeficiency Syndrome (AIDS).

Patients with HIV require Pap smear at time of diagnosis, and then every year (annually) thereafter (asked on Obgyn forms).

Normally, Paps are performed every three years from age 21, and then every 5 years from age 30 with HPV co-testing.

No vaccine due to ­­ antigenic variation (i.e., >7 genotypes and 80 subtypes of HepC exist).

The USMLE might give you a patient with CD4 count of 47 who has ring-enhancing lesion of the brain who is taking HAART and TMP/SMX. Diagnosis is primary CNS lymphoma; Toxo is wrong. The way we know Toxo is wrong is because the patient is on TMP/SMX prophylaxis, which is the prophylaxis for both Pneumocystis and Toxo. Commencing TMP/SMX at a CD4 count of 200 for PJP is “two birds with one stone” by the time the patient gets to CD4 of 100, which is when Toxo comes in. It’s only patients who aren’t on TMP/SMX by the time they fall to CD4 of 100 who get Toxo.

HIV can cause focal segmental glomerulosclerosis (FSGS), a nephrotic syndrome. When HIV leads to renal disease, it is called HIV nephropathy. It is almost always FSGS.

MMR vaccine is live-attenuated and is contraindicated during pregnancy due to theoretical risk to the fetus. If a woman inadvertently receives the vaccine while pregnant or within the month prior to pregnancy, it is not an indication for abortion, but risks to the fetus are increased and proper monitoring is important.

The vaccine is not contraindicated in HIV. Literature says subjectively can be implemented in patients who are severely immunocompromised with consideration of CD4 count, but there is no specific CD4 cutoff. The point is, MMR vaccine is avoided in pregnancy, but not avoided in HIV.

Once CD4 count falls below 200/μL, patients are started on trimethoprim/sulfamethoxazole (TMP/SMX) for Pneumocystis jiroveci pneumonia (PJP) prophylaxis.

TMP/SMX is also the treatment.

Spread usually by Aedes mosquito.

Causes flu-like illness + thrombocytopenia (bleeding gums, petechiae, etc.) + severe joint and abdominal pain.

Hepatocellular damage is due to T cells / death is due to T-cell-mediated apoptosis, not direct viral cytopathicity. This is the highest yield point for HepC on USMLE.

AIDS complex dementia (presents as wet, wobbly, wacky, similar to normal pressure hydrocephalus). Can occur at CD4 counts <50-100.

Spread usually by Aedes mosquito.

Causes microcephaly in neonates if mother exposed while pregnant.

Requires hepatitis B in order to infect, which can be due to co-infection (happening at the same time) or superinfection (occurs later in someone who already has HepB).

If USMLE asks how to prevent HepD infection, answer = vaccination against hepatitis B. There is no vaccine against HepD.

Apparently HepB antigen forms the envelope for HepD (i.e., forms a circle around HepD).

Toxoplasmosis comes in with CD4 count under 100. Prophylaxis is TMP/SMX, the same as for PJP, so often times, once TMP/SMX is appropriately commenced at CD4 of 200 for PJP, it’s already “two birds with one stone,” so we don’t have to worry about Toxo prophylaxis later.

However the treatment for Toxo is sulfadiazine + pyrimethamine. For Pneumocystis TMP/SMX is both the prophylaxis and treatment. NBME asks the Tx for toxo on one of the forms, where TMP/SMX is also listed and wrong. So you need to know the prophylaxes + treatments for Toxo and PJP.

Causes a cutaneous T-cell lymphoma, known as mycosis fungoides, which appears like a skin rash.

If this extends to the blood as a T-cell leukemia, it is now called Sezary syndrome. Sezary syndrome usually presents with diffusely red skin, called erythroderma.

Both mycosis fungoides and Sezary syndrome are characterized by cerebriform-shaped cells on light microscopy.

HTLV can also cause an obscure condition called tropical spastic paraparesis, which is antibodies against neuronal cells leading to otherwise unexplained neurodegeneration over weeks to months.

HTLV causes a cutaneous T-cell lymphoma, known as mycosis fungoides, which appears like a skin rash.

If this extends to the blood as a T-cell leukemia, it is now called Sezary syndrome. Sezary syndrome usually presents with diffusely red skin, called erythroderma.

Both mycosis fungoides and Sezary syndrome are characterized by cerebriform-shaped cells on light microscopy.

HIV can lead to chronic diarrhea caused by Cryptosporidium parvum, whereas immunocompetent patients clear it. C. parvum is a protozoan (unicellular eukaryote).

Under CD4 counts of 50-100, Mycobacterium avium intracellulare and CMV infections can occur. MAI causes lung infections similar to TB, and also sometimes GI infections. CMV causes retinitis. Blurry vision in an HIV patient is CMV retinitis till proven otherwise.