Sunday, April 01, 2007

Definition of Hereditary Spherocytosis

Yep, it's official: mom passed it on to baby.

Hereditary spherocytosis: A genetic disorder of the red blood cell membrane clinically characterized by anemia (Kirsten's entire life), jaundice (yellowing) (Amelia had this at birth) and splenomegaly (enlargement of the spleen) (Kirsten had an ultrasound last month confirming an enlarged spleen).

In HS the red cells are smaller, rounder, and more fragile than normal. The red cells have a spherical rather than the biconcave-disk shape of the normal red cell. These rotund red cells (spherocytes) are osmotically fragile and less flexible than normal red cells and tend to get trapped in narrow blood passages, particularly in the spleen, and there they break up (hemolyze) leading to hemolytic anemia.

The clogging of the spleen with red cells almost invariably causes splenomegaly. The breakup of the red cells releases hemoglobin and the heme part gives rise to bilirubin, the pigment of jaundice. The excess bilirubin leads to the formation of gallstones, even in childhood, There is also often iron overload due to the excess destruction of iron-rich red cells.

Hereditary spherocytosis is most common in people of northern European ancestry. It often shows up in infancy or early childhood, causing anemia and jaundice. The bone marrow has to work extra hard to make more red cells. So, if in the course of an ordinary viral illness, the bone marrow stops making red cells, the anemia can quickly become profound. This is termed an aplastic crisis.

Laboratory studies show evidence not only of many spherocytes but also increased numbers of reticulocytes (young red blood cells), hyperbilirubinemia (increased blood levels of the jaundice pigment bilirubin due to the breakup of the red cells) and increased osmotic fragility of the red cells.

HS is due to a deficiency of a protein called ankyrin. Ankyrins are cell membrane proteins (thought to interconnect integral proteins with the spectrin-based membrane skeleton.) The ankyrin of red blood cells (erythrocytic ankyrin) is called ankyrin-R or ankyrin-1. It is represented by the symbol ANK1.

The HS gene, that for ANK1, has been mapped to chromosome 8 and, specifically, to chromosome band 8p11.2. HS is inherited as a dominant trait so, if a person with HS reproduces, their child (irrespective of whether it is a boy or girl) has a 50:50 chance to have HS (At least Amelia got Gene's blue eyes).

The treatment of hereditary spherocytosis is to remove the spleen (splenectomy). Although the red cell defect persists, the breakup of the red cells (hemolysis) ceases. Splenectomy, however, is a hazard in young children. Young children without a spleen are at increased risk for overwhelming sepsis (bloodstream infection), particularly with the pneumococcus bacteria. Splenectomy is therefore usually postponed if possible until the age of 3 years. Before having a splenectomy, anyone with HS should have the pneumococcal vaccine. Persons with HS (or another cause of brisk ongoing hemolysis) should take supplemental folic acid.

The prognosis (outlook) after splenectomy is for a normal life and a normal life expectancy.


Oh well; I've lived up to this point undiagonosed. This way she'll have an explanation instead of all the mystery.


Regan said...

I agree, better to know. She is soooooo beautiful! Look out once they get the feel of standing up all they want to do is go go go!

Jody said...

I know this is a disease, but it is infinitely interesting. How amazing are our bodies? Thanks for sharing this with us; who knows...maybe someone reading will recognize the signs and be tested.

Your little girl is just as sweet as anything. She is growing so fast! Better get your track shoes ready!

ceytha B said...

So...what does this mean? Are you having surgery? Is Amelia having surgery? Are you both doing well? Are you bummed or relieved to know? Is there an association or support group? You're having an amazing life, there's no reason to think Amelia won't have one too? Right?

Gene & Kirsten said...

All is well with our health. No need for surgery at the moment and no reason to believe we will need any in the future.

Lisa said...

What a pretty girl Amelia is! Love when the blog is updated - love to hear how she is doing and watch her grow in her photos! Keep it up!!!! :)

Joanne Ward said...

Very interesting comments. It sounds like you have done a lot of research and are well informed. Now you can go about life. Amelia is so beautiful, you are going to have your hands full. You all look great, hopefully if you make it to Kodiak we can connect. Not sure we will be coming that way again this year. Enjoy your new family give her a hug for me. Take care.