Thread by @AnandJag1

Hey #medtwitter, #medstudenttwitter, let’s re-visit the topic of Polycythemia!

I saw a number of patients with polycythemia recently, so for this #tweetorial, we’ll look at it from a generalist’s perspective and describe a schema algorithmically. Let’s go!

1/First, let’s remind ourselves that polycythemia itself isn’t a diagnosis. Like many things, it is a condition with an underlying cause.

How we define polycythemia:
-Male: Hb>16.5 g/dL, Hct>49%
-Female: Hb>16.0 g/dL, Hct>48%

2/But wait! Remember that a one-off value won’t cut it. Tempo and delta are key to dx.

Look back in the chart. Is this new or a trend? If new, make sure you check at least one additional Hb AND make sure to account for potential hemoconcentration.

3/Great, now that we’re sure this is polycythemia, we may ask why are there so many RBCs?!

Instead, pause, and try asking, “what stimulates our body to produce more RBCs?”

Erythropoeitin! a.k.a EPO. Check a level.

4/While you’re waiting for the EPO level, check if your patient needs rx first and dx second.

Too many cells in the circulation = risk of hyperviscosity.

Ask some questions centered around the most frequently affected systems: neuro, heme (bleeding), CV

5/Hyperviscous? Better call hematology. This patient may need urgent plasmapheresis, phlebotomy, or chemo.

Not hyperviscous? Sweet, we have some time, let’s see what came of that EPO level.

6/Most polycythemia comes in two general flavors:

- EPO-independent (primary) -> something else is driving RBC production
- EPO-dependent (secondary) -> something is ramping up EPO levels

7/Primary polycythemias

Typical issue: mutations
EPO levels: realllly low.

Acquired: polycythemia vera (JAK2 V617F) and MPNs (MPL, CALR, also JAK2)
Inherited: honestly, this list is long and obscure, and I don't know. Look it up 😊

8/Secondary polycythemias

Typical issue: oxygen (delivery/sensing) vs tumor vs exogenous
EPO levels: normal/high

Categories:
- Chronic hypoxia & bad oxygen sensing (at kidneys)
- Some tumors produce EPO
- Some people put things into their bodies

9/Note about 2ndry causes

Many of these conditions can be screened for with a good history! Even though you’ll do a good workup, think about common co-morbids that can drive this disease.

10/Finally, it’s always a good idea to call your friendly neighborhood hematologist if you’ve made a diagnosis or if you’re stuck. As with many disease processes, there can be a spectrum and overlap. Best to have an expert around to help.

11/Summary:

- Polycythemia = too many RBCs; confirm the measurement!
- EPO is key
- Primary causes -> mutations
- Secondary causes -> oxygen delivery/sensing, tumors, or exogenous substances
- take a good history and watch for hyperviscosity!

12/Thanks for joining in this exercise, #medtwitter, #medstudenttwitter!

Big props to @Anand_88_Patel for his input. Check out his #tweetorial:

https://twitter.com/Anand_88_Patel/status/1184116423796416518

I welcome any thoughts and feedback. Help make this better!
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