USMLE® Step 1 style questions USMLE
A 30-year-old woman comes to the clinic because of fever and fatigue. She has no chest pain, cough, sore throat, or hemoptysis. She works as a nurse practitioner in a nearby hospital. Five months ago, she was injured by a needle from a hepatitis patient. She also has Hashimoto's thyroiditis and receives replacement therapy. Her temperature is 38.5°C (101.3°F), pulse is 100/min, respirations are 15/min, and blood pressure is 110/70 mm Hg. Physical examination shows jaundice and right upper abdominal quadrant tenderness. Laboratory studies show:
Which of the following is the most likely diagnosis?
Content Reviewers:Rishi Desai, MD, MPH
Contributors:Tanner Marshall, MS
So an autoimmune disease is this special sort of disease where your own immune cells have gone rogue and start to attack your own cells, right?
Hepatitis happens to mean inflammation of the liver, so it’s reasonable to say that autoimmune hepatitis is this resulting inflammation of the liver tissue because they’re being attacked by your own immune cells.
Like many autoimmune diseases, the root cause of autoimmune hepatitis is ultimately not super clear, but some researchers think it’s a combination of environmental triggers and genetic predisposition.
It tends to occur most often in young women, and the female to male ratio is around 4:1.
Also though, an important piece of the genetic puzzle is the human leukocyte antigen system, shortened to HLA, which is this location of genes on chromosome 6 that regulate our immune functions.
Specifically, these genes control the proteins that are encoded and used on the cell’s surface to present foreign molecules to the immune system, so although they present antigens, they’re also a form of antigen themselves, but they aren’t the same type of antigen as one on an infectious molecule, but actually alloantigens that vary from person to person and are our specific “self-proteins”.
Usually, our thymus makes sure the T cells that attack these self proteins aren’t allowed to survive, in autoimmune disease, there may be some abnormality associated with specific self-proteins that lets the T cells attack.
Based on studying people with autoimmune hepatitis, they often have HLA- DR3 and DR4, which are both MHC class II surface receptors.
The DR part refers to its location on the chromosome, for example, depending on the location, you could have HLA-A, HLA-B, HLA-C or HLA D, and HLA-D has three subregions: P, Q, R, so this one is HLA-DR.
So there seems to be some sort of connection between these particular “self-proteins” and mounting an attack against your own liver.
Autoimmune hepatitis also tends to be associated with other diseases like Hashimoto’s thyroiditis, where your immune cells attack your thyroid, and Grave’s disease where your thyroid overproduces thyroid hormones.
Clinically, autoimmune hepatitis patients can sit anywhere on a spectrum from completely asymptomatic to cirrhosis and fulminant hepatitis, also known as acute liver failure, or they might be somewhere in-between with debilitating symptoms like fever, jaundice, and hepatosplenomegaly, a condition where both the spleen and liver are way larger than their normal size, probably caused by inflammation due to immune cell attack.
Also, for symptomatic patients, there’ll likely be an increase in blood transaminases.