Like many young women her age, my daughter recently received information about Gardasil, a vaccine that offers protection against some types of the human papilloma virus (HPV). HPV is a virus that infects the skin & mucous membranes. It comes in more than 100 forms, some of which cause things like warts (including genital warts). Others are implicated in various cancers, including cervical cancer (which is where Gardasil comes in).
Warts on the skin, particular on hands & feet, are fairly common. Most of us aren't bothered by them (although 'plantar warts' - those on the soles of your feet - can make walking painful. I know, having had them!), because our immune systems keep them pretty much under control. But in rare individuals the immune system can't manage to destroy the virus-infected cells, & this can lead to some bizarre & unfortunate outcomes.
What sparked these musings? A report on the 'tree man of Indonesia', a man called Dede Kosawa who has such extreme warty overgrowths on hands & feet that he can neither walk properly nor use his hands.
Dede first came to the world's attention in late 2007, when doctors began a series of operations that were to remove more than 6 kilograms of warty hummocks & tendrils from his extremities. When he returned home in August last year, the doctors hoped that a combination of the surgery & high-dose vitamin A would see him able to lead a fairly normal life. Unfortunately this hasn't happened, & they now say Dede will need twice-yearly operations for the rest of his life to keep the growths under control.
The technical name for Dede's symptoms is epidermodysplasia verruciformis, which appears to be due to an autosomal recessive mutation. Two genes on human chromosome 17, called the EVER1 & EVER2 genes, appear to be implicated in the cell's transport & use of zinc. Zinc is a cofactor for some viral proteins, & seems that these 2 genes are involved in blocking viral access to the cell's zinc. So mutations that inactivate one or both of these genes may leave the body open to epidermodysplasia verriuciformis, because the virus is able to use cellular zinc stores & grow beyond the immune system's ability to control it. Thankfully, the mutation is rare - but this is cold comfort to those few individuals who inherit two mutated EVER alleles and consequently suffer from this disfiguring disease.