A Simple Case of Vampirism
"Watson, if it should ever strike you that I am getting a little over-confident in my powers, or giving less pains to a case than it deserves, kindly whisper 'Norbury' in my ear, and I shall be infinitely obliged to you." - Sherlock Holmes, The Yellow Face
The diagnosis: Erythropoetic protoporphyria
Working backwards: When Chase made the diagnosis of erythropoetic protoporphyria, he did so working on the assumption that the patient's allergic tendencies could be attributed to light exposure. Based on the Harrison's textbook, the first two lab studies to check when a patient is sensitive to light is a plasma porphyrin (to rule out porphyrias) and an ANA/Ro/La (to rule out lupus and other similar autoimmune processes). Even though Chase didn't order either of these studies, it makes sense that he presumed that one of these two diseases was leading to the patient's symptoms once he made the connection to the light. Had he ordered the tests, he would have found increased levels of plasma porphyrin. Some of the common porphyrias are porphyria cutanea tarda (#1), erythropotoetic protoporphyria (#2), and acute intermittent porphyria. If you tested the urine for porphyrins, porphyria cutanea tarda would show a normal porphobilinogen level and an increased uroporphyrin and 7-carboxylate level; erythropoetic protoporphyria would show normal porphyrin and porphyrin precursor levels; and acute intermittent porphyria would show increased levels of porphobilinogen.
Loose ends:
Q: If the disease is genetic, why don't either of Alice's parents show symptoms of the disease?
A: The disease is autosomal dominant, which means that even one copy of the gene should give you symptoms. However, some people with only one copy of the gene have been noted to have no symptoms, so there is a documented variation in the severity of the disease.
Q: Why was a diagnosis of pancreatitis thrown around early in the episode after the patient presented with abdominal pain?
A: Generally, when a doctor says that a patient likely has pancreatitis, he or she does so based on a blood sample that shows increased levels of amylase and lipase. Because pancreases make amylase and lipase to help digest food, damage to the pancreas breaks down individual pancreatic cells and releases these enzymes into the bloodstream, thereby elevating their levels in the blood. A CT scan could then be performed 48 hours after the onset of symptoms, with the goal to try to visualize some kind of fluid or cyst in the pancreas. I'm assuming then that this diagnosis was made because Alice was experiencing excruciating abdominal pain and had increased levels of amylase and lipase. Erythropoetic protoporphyrias are actually associated with gallstones (composed of insoluble crystalline protoporphyrin), which could have lodged in the common bile duct (like the one in the picture), creating a blockage of the main pancreatic duct and increasing the risk for pancreatitis.
Q: When Alice first developed a rash on her arm, why was it attributed to thrombocytopenia?
A: Thrombocytopenia is a low level of platelets, which can result in a petechial rash. From way up in the surgery viewing booth, it's possible that the patient's rash looked petechial in nature (like in the picture). I can't really think of a better explanation because I don't think a blood test was every run to confirm or reject this idea. Petechiae generally appear as small little dots.
Q: What things besides pancreatitis (and other anatomical diseases like appendicitis) can lead to abdominal pain, like the kind that Alice had?
A: There's a mnemonic I use from the Saint-Frances Guide to Inpatient Medicine to remember all the non-typical causes of abdominal pain.
Puking My BAD LUNCH.
Porphyria
Mediterranean fever
Black widow spider bite
Addison's disease, Angioedema
Diabetic ketoacidosis
Lead toxicity
Uremia
Neurogenic
Calcium high
Herpes Zoster
Q: Did vampires suffer from porphyria?
A: There is some thought that legends of vampires were based off of people who suffered from porphyria. Porphyria causes severe rashes when a person is exposed to sunlight, and one way to treat porphyrias is to transfuse blood products. Centuries ago when blood products weren't readily available, it would be theoretically possible to receive blood by drinking it straight from a victim's neck veins. Here's an interesting article that goes more into depth on the topic.
6 Comments:
Commenting was turned off in your most recent post, so I'll post the comment here :)
Hurray~! You updated! Thanks so much for taking the time to write in this blog, I find it all so fascinating! I've been lurking on here for a while now.
Good luck on your medical studies!
Thanks for the kind words. I had been lost in the grips of my surgery rotation, so I had tuned out for a bit.
What I want to know is, why would they come up with EPP if it is not associated with abdominal pain and paralysis. It would more likely be VP or HCP, which do present with those symptoms, plus the photosensitivity. Who on the research team went on vacation for that episode?
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great post. I would love to follow you on twitter.
This has been on my mind for some time..... It does lead to other issues...
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