Tuesday, November 13, 2007

A good time to be a gene hunter

Two interresting mutations have popped up this week. Unfortunately neither will turn you into a hero...


This man has some kind of mutation which rendered his immune system unable to control the warts growing as a result of an HPV infection. Another reason to get the HPV vaccine! The doctors have proposed to use high doses of vitamin A to stop the warts, and remove the rest by surgery.


This 7ft tall 12 year old, had all his teeth by 4 months and was already has big as a 12 year old by the time he got to kindergarden. This is not a case of gigantism, which occurs because of pituitary tumours excreting too much growth hormone, rather this seems to be a new kind of mutation. Joining the 50 or so different genetic syndromes which cause excessive growth such as:

"Extra sex chromosomes (beyond the normal two) with therefore extra copies of the SHOX gene (beyond the normal two) usually results in enhancement of height growth. The most common of these karyotypes are 47,XXY (Klinefelter syndrome), 47,XYY, and 47,XXX. The added height increment is usually modest.

A very rare but more extreme version of "eunuochoid" tallness occurs when a mutation of the estrogen receptor reduces the response of the bones to estradiol. Estradiol is a byproduct of testosterone in both males and females, and is the most potent accelerator of bone maturation and closure known. If a person fails to respond to estrogen, growth can continue until late-20s or longer, and the affected person can reach 8 feet or more in height. Estrogen resistance is the only other endocrine condition that can rival growth hormone excess in producing gigantism. In contrast, the tallness associated with the more common androgen insensitivity syndrome averages only a few inches, as estradiol is not produced directly but rather through conversion from androgens by aromatase.

Marfan syndrome is an uncommon genetic disease due to an inherited defect of connective tissue. In addition to moderate tallness, persons with this condition usually have a slender body build with unusually long fingers (arachnodactyly). Many can also develop a dislocaton of the lens of the eye or, more seriously, a progressive deterioration of the walls of the aorta which can result in sudden death in adulthood. It is usually inherited as an autosomal dominant trait.

Sotos syndrome resembles acromegaly in its mild distortion of facial growth. In addition to tallness, the chief characteristics are large head size, slow development, and autosomal-dominant inheritance."


5 comments:

The Doc said...

Marfan's is actually quite interesting. Because there is a connective tissue fault, the sacs which surround the bones (and restrict their growth) don't slow the growth of the bones, and give you a large (and elongated) body.

It's also why their aorta pops, and they get dislocations. It's rare for them to live much past 20-25.

kamel said...

"Another reason to get the HPV vaccine!"

I'm certainly no immunologist (and the article is vague about the exact nature of his mutation) but with this defect that he has, would a vaccine be effective?

Kari H said...

To "The Doc"... it is NOT unusual for Marfab;s patients to live well into their 70's. Nowadays, they're lifespan is usually just as long as the typical person, provided they are under care of a physician.

Kari H said...

Sorry, that's Marfan's... finger slip!

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