Things I've Learned: HLH, Blood Vessels, & Hummingbird Bobtail Squid

One good thing about the sometimes overwhelming volume on the internal medicine service is that residents get no shortage of clinical exposure. Though sometimes I feel like I'm doing busy work rather than learning, there's no doubt that every single patient encounter reinforces the increasingly familiar patterns of management, if not teaching me something completely new. Here's one of those new things and a couple of others that I've found interesting this week:

1. hemophagocytic lymphohistiocytosis (HLH) -- A bone marrow biopsy on a lymphoma patient returned this week showing HLH, an uncommon hematologic disorder I'd never even heard of. It's one of the cytokine storm syndromes where benign lymphocytes and macrophages proliferate, secreting large amounts of inflammatory cytokines, leading to severe and life-threatening hyperinflammation. HLH can be acquired after strong immunlogic activation, caused by things such as infection, immunodeficiency, or malignancy. It may also be familial and in 70% of cases occurs before the age of one. Patients present with fever, splenomegaly, pancytopenia, elevated LFTs, markedly elevated CRP/ESR/ferritin, and bone marrow biopsy demonstrating histiocytosis. Treatment regimens include ivIg and high dose prednisone.

   

   HLH bone marrow -- demonstrating RBCs in the cytoplasm of macrophages
   (http://en.wikipedia.org/wiki/Hemophagocytic_lymphohistiocytosis#mediaviewer/File:Haemophagocytic_lymphohistiocytosis_Bone_marrow.JPG)

2. 96,000 km of blood vessels -- I came across a wealth of interesting facts from reading All the Light We Cannot See several weeks ago. One impressive one was that the human body contains approximately 96,000 km of blood vessels! That's more than twice the circumference of Earth!!

   

   a particularly memorable blood vessel figure at Body Worlds
   (http://photos.nj.com/star-ledger/2013/04/preview_of_body_worlds_pulse_3.html)

3. hummingbird bobtail squid (Euprymna berryi) -- This 3-cm beautifully iridescent mollusc inhabits the waters from Indonesia to the East China Sea. Its glow is actually from a bioluminescent bacteria, Vibrio fischerae, with which it shares a mutualistic symbiotic relationship. About a trillion V. fischerae reside in a chamber called a "light organ" inside the squid's mantle, nourished by a sugar and amino acid solution that the squid produces.

   

   hummingbird bobtail squid
   (http://www.australiangeographic.com.au/blogs/creatura-blog/2014/12/hummingbird-bobtail-squid)

What's something interesting that you learned this week?