Radiation is actually a big deal. Here, say
that your patient has a DNA repair issue.
And it produces pyramidine dimers leading to transcriptional
errors and mutations of oncogene. In other words,
we'll talk about this. I'll show you a picture coming up
where the thymine dimers remain within your DNA.
Thymine dimers or dimers normally should be
removed by excision type of enzymes.
But in a condition known as xeroderma pigmentosa
in which the excision repair genes have been damaged.
The thymine dimers remain within the DNA.
Upon exposure, to UVB rays,
which are the dangerous type of ultraviolet rays, the
patient may then develop any type of skin cancer
with xeroderma pigmentosa. What do you mean by
any type? Three major types. A melanoma perhaps.
A squamous cell cancer of the skin perhaps, or even basal cell
carcinoma. Be careful. Here we have an issue with our DNA repair gene.
It is a nucleotide excision repair pathway
which has been, k/o means knocked out.
So what's a recessive inherited disease that we are talking about here
in which the nucleotide excision repair genes has been knocked out.
Xeroderma Pigmentosa. What happens? Here is a thymine dimer.
You should have an endonuclease which comes in and this is normal.
It should repair it. And upon repair, you then have ligases,
that move in a 5' to 3' polymerase activity.
Therefore, that which has been excised, has now been rejoined
by ligase. Guess what happens in xeroderma pigmentosa.
It does'nt occur. These repair enzymes are mutated.
They are not present. So therefore,
the thymine dimers will remain within the DNA. Now what's
next? The patient has now been exposed with UVB rays.
Wow. Further mutations take place, developing cancer.
Other carcinogens that you need to know for sure.
Non-ionizing radiation may result in malignant
melanoma. May result in basal cell carcinoma.
What you are seing here in this picture, is by the eye.
A corner of the eye, with a basal cell carcinoma.
I want you to take a look at the characteristic of a basal cell
carcinoma. I want you to begin the process of reinforcement now.
If this is the first time that you have ever seen basal cell
carcinoma, you'll notice there is a central crater here.
It looks like a volcano. The basal cells have been affected
in the skin here. Non-ionizing type of radiation.
It's almost always a benign tumor. It will almost never metastasize.
Interesting enough, when I set up the foundation for you,
when I talked to you about benign, what did I tell you
about size of that tumor? Small. Here is an exception.
Basal cell carcinoma, you let this linger it gets bigger,
bigger, bigger. Does it metastasize? Almost never.
But it does'nt mean it does'nt destroy the face.
It will. Completely disfigures the face.
If you've ever seen elderly patient with basal cell carcinoma
upon exposure to UV ray, it can be pretty nasty.
So just because it's benign does'nt mean it's not dangerous.
It can still get pretty big and cause localized damage.
Keep that in mind. Aggresive. Third degree burns. Now, pay
attention here. Your patient, suffered a third degree burn,
and resulted in a cancer? Yeah. There could be so much
physical trauma that with enough irritation,
that could be enough of a mutation and irritation, in which
the patient now develops cancer of that particular organ.
Not only could you have your third degree burns
giving rise to squamous cell cancer of the skin,
which is really seriously unbelievable isn't it. But, what if
the patient has osteomyelitis, if immunocompetent maybe Staph.
If you have something like sickle cell disease maybe
Salmonella osteomyelitis. Or you stepped on a nail
and Pseudomonas got in. That's a bone infection. And what's
that bone infection it's going to then drill a sinus
into the bone. A sinus within the bone is draining. And
that draining sinus may then develop, unbelieveably,
squamous cell cancer of the sinus. Actual physical trauma
with enough persistant irritation may result in cancer.