4Q Chromosome Duplication



A picture of a typical set of chromosomes.



Humans are physiologically created based off of our genetic material packaged in chromosomes, our genetic blueprint. We typically have 46 chromosomes, 23 coming from our mother paired with 23 coming from our father. Our bodies are designed to read the blueprint from the 46 chromosomes that have just the right amount of genetic material. When we have extra (or lack some) genetic material, physiologically things can go a little haywire.

Our sweet baby Matthew was diagnosed with extra genetic material on his 4th chromosome. His official diagnosis is "4Q Chromosome Duplication" or "Partial 4Q Trisomy". Q indicates it is on the bottom section (or arm) of the 4th chromosome and the genetic material duplicated is from sections 25-34.2. This is a very rare chromosome disorder. When we met with genetics in April 2010, they originally thought his duplication was a bit different and there was one other case.  At his 2 year check, when we discussed the more refined results of the microarray, the geneticist believed Matthew was the only known person in the world with his particular duplication.

What caused Matthew's 4q duplication? We don't know. His duplication is 'de novo', meaning neither Darren nor I (Katie) have an abnormal 4th chromosome. A geneticist has compared chromosome duplications (which occur during meiosis) to trying to type from a page, where you may type a duplicate line if your eyes don't follow to the next line. It's just a chance happenstance. Dumb luck.

What does this mean? Honestly, we don't know and no one really does. With only similar but not exact cases to reference, we cannot extrapolate. As well, even identical twins born with identical duplications can exhibit different symptoms, so Matthew will write his own story based off of his unique combination of genes.
 

So far, we know Matthew has several uniquenesses that have resulted from his additional genetic material.

Matthew has
-missing thumbs
-mild to moderate hearing loss left ear
(As of 8/17/10, Matthew's hearing tested "normal" in both ears!)
-microtia (malformed, small) right ear
-heart abnormalities: ASD(Healing), functional biscupid Ao valve, dialated arortic root, PDA (Fixed via surgery 10/7/10), LVH (Healing)
-only 1 kidney (ectopic fused horseshoe kidney)
-undescended testes and hernia (Fixed via surgery 6/1/11)
-urachal cyst
-malrotated intestines (Fixed via surgery 7/27/10)
-low muscle tone
-slight torticallous (outgrew by 1 yr)
-micrognathism (small chin)
-GERD/reflux (outgrew by 15 months)
-global mild developmental delays
-craniosynostosis (Fixed via surgery 12/06/10)
-atypical venous structure
-throat anomalies: laryngomalacia, tracheomalacia, and subglottic stenosis
-gastroparesis (Periodically)

We don't know what to expect from Matthew...he's one in billions. What we do know is that we will do everything in our power to help him grow into his greatest potential. He has amazed us thus far!

Below are some helpful links about 4Q chromosome duplications.
--Unique is a rare chromosome disorder support group, based in the UK. To read Unique's article about 4Q duplication, click here.
--For a tour of the basics relating to chromosomes, click here.
--The genetics home reference is a good resource for basic information on chromosome 4. They have a nice diagram of the chromosome and you can see the areas that Matthew has duplicated (25-34.2). To see the diagram, click here.
--For information on the genes identified on 4Q, click here.

We continue to update our blog with the latest information about Matthew and all of us at the Hoy House. We are unbelievably blessed with fantastic, supportive friends and family. Thank you for the positive thoughts and prayers for Matthew and for us.

(Apologies to the scientific-minded folks as this is an oversimplification of genetics!)

A picture of Matthew's chromosomes.
The arrow indicates the chromosome (4) with the additional genetic material.