USMLE® Step 1 style questions USMLE
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A 44-year-old musician comes to the office because of abdominal pain for 3 months. He has not been to a physician in 10 years, and has been using IV drugs since age 17. He does not drink alcohol and has no significant family history. His temperature is 38.0°C (100.4°F), pulse is 99/min, respirations are 18/min, and blood pressure is 117/78 mm Hg. Examination shows a large distended abdomen, yellow sclera, palmar erythema, and spider angiomata diffusely on his abdomen and extremities. Lab results reveal: Hepatitis A IgM: negative, HBsAg negative, Hep B anti-HBc antibody: negative, Hep B anti-HBs antibody: positive, and Hepatitis C Abs test: positive. Which of the following describes the genome of the most likely pathogen responsible?
Content Reviewers:Rishi Desai, MD, MPH
Contributors:Tanner Marshall, MS
Hepatitis, meaning like this inflammation, of the liver, most commonly comes about because of a virus.
These viruses tend to target the cells in the liver, and when they get in and infect these cells, they tend to cause them to present these weird and abnormal proteins via their MHC class 1 molecules, and at the same time, you’ve also got these immune cells infiltrating the liver and trying to figure out what’s going on, and so the CD8 positive T cells recognize these abnormal proteins as a sign that the cells are pretty much toast, and the hepatocytes go through cytotoxic killing by the T cells and apoptosis.
Additionally though, patients might have hepatomegaly, where their liver is abnormally large from inflammation, which might cause some pain.
Also, as more and more damage is done to the liver, the amount of transaminases in their blood will increase.
Your liver has these transaminase enzymes so it can do its job of breaking down various amino acids.
Typically the serum amino transaminase, or the amount in your blood, is pretty low, but when your hepatocytes start getting damaged they start leaking these into the blood, so a common sign is a greater amount of both alanine aminotransferase, or ALT, and aspartate aminotransferase, or AST, typically even though both are elevated, ALT will be greater than AST in viral hepatitis and will also be the last of the two liver enzymes to return to normal.
Also, elevated levels of atypical lymphocytes are common to see with viral hepatitis, known as atypical lymphocytosis.
The lymphocytes are usually like huge, very large, due to stimulation from antigens, in our case the hepatitis virus antigens.
When things progress to cirrhosis, there may also be increased urobilinogen in the urine.
However, with cirrhosis, liver cells aren’t working properly anymore, so there’s a lot of liver fibrosis, so hepatocytes can’t process the urobilinogen, which is redirected to the kidneys and excreted, so you end up with more urobilinogen in your urine.
Now there are five known flavors or types of hepatitis virus, that have slightly different and unique properties.
Hepatitis A virus, or HAV, is almost always acute only, and there is essentially no chronic HAV.
If we’re talking serological markers, an HAV-IgM antibody indicates an active infection, whereas HAV-IgG antibody is a protective antibody and tells us that there’s been recovery from HAV or vaccination in the past.
Hepatitis E virus’s actually pretty similar to HAV, with the same route of transmission, oral-fecal, and is most commonly acquired through undercooked seafood or contaminated water.
Two big differences to note though between these two guys, is that (1) only HAV has the option for immunization and (2) HEV infection for pregnant women can be very serious, and can lead to acute liver failure, also sometimes called fulminant hepatitis.
Alright next on the docket is Hepatis C virus, this guy is transmitted via the blood, so could be from childbirth, intravenous drug abuse, and there’s also a small chance of getting it through unprotected sex, if there are open lesions, like cuts or sores, in the genital area.
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