Rh Disease – Sweet, Sweet Blood Cells – Part 2

Posted by on Aug 4, 2015 | 0 comments

Welcome back!  Click here for Part 1.  Last time we left off with mom’s body sending anti-RhD antibodies through the placenta to her second baby.

What happens to baby? 

In all cases of Rh disease, baby loses some RBCs – in fact, baby’s own immune system destroys the RBCs because they were marked with maternal antibodies.   What happens next depends on how many antibodies baby was exposed to.

In mild cases, baby has slight anemia – too few oxygen-carrying RBCs.  Baby might show no symptoms at all.

Baby might develop jaundice1 after he’s born.  When RBCs are destroyed, they release their hemoglobin.2  Baby starts to break down the hemoglobin so he can recycle the iron, and one of the breakdown products is a yellow substance called bilirubin.  In large amounts, it can damage baby’s brain.  While he’s still in the womb, baby passes the bilirubin back to mom’s liver for disposal.  However, right after birth, mom is no longer taking care of the bilirubin and baby’s liver doesn’t know what to do yet, so the yellow-colored substance accumulates in baby’s skin.  Blue lights break down the bilirubin into small enough pieces that baby’s liver can handle it.3

Blue light breaks up the bilirubin into small enough pieces that baby's liver can digest them.

Blue light breaks up the bilirubin into small enough pieces that baby’s liver can digest them.

In severe cases, baby loses a lot of RBCs.  Baby’s heart is pumping harder and harder to get the remaining RBCs around his body to deliver oxygen.  Sometimes, this effort is too much for the heart and baby dies.

How it’s treated

  1. the yellow-colored skin for which babies are placed under blue lights []
  2. the red, oxygen-carrying protein []
  3. The superficial cause of jaundice is always the same – excess bilirubin in the blood. However, all sorts of things besides blood type differences can cause an excess of bilirubin, some of which may be covered in another post. []
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Rh Disease – Sweet, Sweet Blood Cells – Part 1

Posted by on Aug 2, 2015 | 0 comments

… and, we’re back!  Grad school and life kept me pretty busy in the last year.  The Ebola and Disneyland measles outbreaks almost roused me into writing a post, but it was an article on Rh disease that finally did it.

Do you know your blood type?  I… don’t actually know mine.  Barring emergency circumstances, most people first become acquainted with the complications of blood type when they have a baby.  Certain mothers who are Rh- (“R h negative”) need shots during their pregnancy to protect their next baby.  Which mothers?  Why do they need shots?  Why is it for the next baby?  Let’s dive in!

Blood Types

First, let’s talk about blood types.  Red blood cells (RBCs) are decorated with various sugars for… unknown reasons.1

The most important sugars we call A and B, from which we get the blood types A, B, AB, and O (O means simply the absence of A and B).  The types of sugars on your RBCs determine your blood type.

Blood type is determined by which sugars are on your red blood cells: A sugars, B sugars, both! (AB), or none (O).

Blood type is determined by which sugars are on your red blood cells: A sugars, B sugars, both (AB), or none (O).

The next most important blood sugar is the Rhesus D sugar2, abbreviated RhD or simply Rh.  If you have this sugar,

  1. Seriously, we don’t know why.  See, “Why do we have blood types?” in the Further Reading section. []
  2. discovered using the blood of Rhesus monkeys []
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Fetal Circulation – The Secret’s in the Lungs

Posted by on Jun 25, 2014 | 0 comments

I’m starting a new series about babies called Woven Together because the development of a little person is fascinating. For the most part, this series will deviate from the main content of the blog – how things go wrong – to tell how things go right. I hope you enjoy!

Babies in the womb have to make some adjustments to account for the fact that they’re in the womb: there’s no air to breathe and no food to eat. Today, we’re going to learn how their adjusted circulatory system works.

First off, mother and baby don’t share blood. They have two completely separate circulatory systems.1 Baby’s heart starts beating about 22 days after conception so that he can pump his blood to deliver nutrients to all the parts of his rapidly-growing body. The heart is baby’s first organ to

  1. That’s how mother and baby can have two separate blood types with relatively few problems. []
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Sickle Cell and Malaria – A Double-Edged Sword

Posted by on Jul 29, 2013 | 4 comments

And now for the exciting conclusion to these two posts.  

Disclaimer: I’m not a doctor – just a bioengineer who happens to find pathophysiology fascinating.  If you find an error, please let me know!  Also, NONE of my drawings are to scale.

In this post, we looked at how one tiny change in a person’s DNA caused her to suffer from sickle cell anemia.  We learned that, untreated, about 50% of children with sickle cell anemia die before their fifth birthday.  If you understand natural selection, you’ll recognize this as a puzzle: if sickle cell anemia is so deadly, why are there so many people still affected by it?  Let me explain the puzzle a little further.

For almost all traits, a person has two copies of instructions: one from her father and one from her mother.  Sickle cell disease is autosomal recessive – which just means that both parents must pass on the sickle cell trait for the child to be sick.  People who only received the trait from one parent aren’t sick, but can pass the disease on to their children.

In this case, Mom and Dad are both carriers of a genetic disease.  Statistically, 1/4 of their children will be completely healthy, 1/2 of their children will be healthy carriers of the disease, and 1/4 of their children will be sick.

In this case, Mom and Dad are both carriers of a genetic disease. Statistically, 1/4 of their children will be completely healthy, 1/2 of their children will be healthy carriers of the disease, and 1/4 of their children will be sick.

In most cases where an autosomal recessive trait is deadly early in childhood, the disease dies out.  A child affected by the disease won’t live to have children of his own, and thus won’t pass down the bad information.  With no one to pass it on, the disease stops.

But, sickle cell disease hasn’t followed that pattern. 

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Malaria – An Ancient Struggle

Posted by on May 13, 2013 | 0 comments

Before we discuss why sickle cell anemia has persisted for so long, let’s take a detour to learn about once of the most ancient human diseases: malaria.  

Disclaimer: I’m not a doctor – just a bioengineer who happens to find pathophysiology fascinating.  If you find an error, please let me know!  Also, NONE of my drawings are to scale.

Malaria: scourge of the human race since time immemorial.  The disease is mentioned by the ancient Chinese, Egyptians, Greeks, and Sumerians as far back as 2700 BC.  Some Biblical scholars even believe that Peter’s mother-in-law was suffering from malaria before Jesus healed her.

Unlike the ancient scholars who attributed malaria to the “bad air” (mala aria) of the swamps, we now know that malaria is spread by mosquitoes (who, as it so happens, absolutely love swamps.  You were close, ancient scholars).  But what happens after that terrible bite?  How does malaria make you sick?

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