Diagnosed with ADA and SCID

As the last post told, we found out on the 18th June that Harrison has SCID, caused due to the deficiency of ADA enzyme in his blood.

ADA deficiency is one form of SCID (severe combined immunodeficiency), a type of disorder that affects the immune system. ADA deficiency is very rare, but very dangerous, because a malfunctioning immune system leaves the body open to infection from bacteria and viruses.

The oridnary common cold is potentially lethal to those who suffer from ADA deficiency and SCID.

The disease is caused by a mutation in a gene which codes for the enzyme adenosine deaminase (ADA). Without this enzyme, the body is unable to break down a toxic substance called deoxyadenosine. The toxin builds up and destroys infection-fighting immune cells called T and B lymphocytes. The T-lymphocytes are matured in the Thymus Gland and go around fighting different viruses. The B-lymphocytes are divided further into different cells called immunoglobulins. These are antibodies and fight infection. Harrison's thymus gland is not able to be seen on an x-ray which is a classic sign of SCID.

ADA deficiency is an autosomal recessive disorder. Both parents need to pass the defective gene to their child in order for that child to inherit the deficiency. It is the ADA deficiency that in turn causes SCID.

Because ADA deficiency affects the immune system, people who have the disorder are more susceptible to all kinds of infections, particularly those of the skin, respiratory system, and gastrointestinal tract. They may also be shorter than normal. Sadly, most babies who are born with the disorder die within a few months.

How is ADA deficiency treated? There is no real cure, but some treatments include bone marrow transplant, transfusions of red blood cells, enzyme replacement therapy, gene therapy and transfusions of IG (immunoglobulins).

Interesting facts about ADA Deficiency - ADA deficiency is extremely rare. Only about 1 child in 2 million are affected. Australia have only ever had a handful of cases of ADA - SCID.

Harrison is the first child to be diagnosed with ADA deficiency at the Children's Hospital at Westmead. We are lucky enough to be cared for by a Professor who had diagnosed one other case of this himself.

We are also very lucky that the medical staff at both Gosford and Westmead Kids are so thorough. They picked up that Harrison had ADA deficiency before he started to get repeated infections. I really feel it is because of them that we have Harrison here today and that he was diagnosed so early in the piece. Many kids aren't identified until they are around 6 months old, and who knows what damage can be done in that time with no enzyme to do its job? I don't know how I will ever thank them for all that was done, and I am sure they will continue to do. Hopefully I will find a way to do it one day :)

I had not let my milk supply go, so we started to rebuild my milk supply and complimentary feed Harrison on formula. His weight slowly started to climb again. And his oxygen stats improved so that he was also weaned off oxygen. Harrison was given a dose of Intragam (IVIG) - immunoglobulin transfusion to help boost his immune system. He seemed to pick up a little from the transfusion.

So we are here, with a diagnosis- finally.. and we now go through the hardest part to date. Tissue typing tests to see if the kids are a donor match for Harrison for bone marrow transplant, typing Scott and I for our HLA (antigens), and testing for all of us to see what ADA levels we all have.

A long weeks wait saw that Scott and I are both carriers. Together we had a 1 in 4 chance of having an ADA deficient child. Harrison is the only one affected, while Marlie (5) is unaffected, Sterling (3) and Ella (2) are both carriers but otherwise unaffected.

The other good news from this - Ella is a perfect HLA match - meaning that they matched on all 6 antigens.