What is XP?

       
  • XP is an abbreviation of Xeroderma Pigmentosum

  • XP is a recessive genetic condition, whereby both parents have the carrier gene resulting in a 1 in 4 occurrence rate of them giving birth to an affected child

  • there are 7 known complementation groups of XP (groups XP A-G) plus a further XP-variant grouping (XP-V)

  • XP affects less than 100 people in the UK

  • patients with XP are 10,000 times more susceptible to skin cancer than the general population

  • patients with XP are affected by exposure to  UVA & UVB and must be protected from both

  • ultraviolet radiation (UVR) from UVA & UVB covers the spectrum of 290-400 nm (nanometres) and it is this range of light that must be avoided

  • UVC is the wavelength of 100-290 nm, however this is mostly absorbed by the atmosphere and ozone layer so presents no real risk

  • 30% of XP patients suffer a degree of neurological involvement which is believed to be unrelated to UV exposure

  • there is currently no cure for XP.
[Image illustrated by Michael Howdon, Copyright Nicola Miller 2015]


Xeroderma Pigmentosum (XP) is a very rare genetic condition characterised by an extreme sensitivity to ultraviolet radiation (UVR) which affects less than 100 patients in the United Kingdom and equally low numbers around the world.

Patients with XP lack the DNA repair mechanism to repair damage caused to the skin by exposure to ultraviolet (UV) light, in particular UVA and UVB.

The primary cause of exposure to UV is through exposure to daylight and this light is made up of two types of harmful rays that reach us. Long wave ultraviolet A (UVA) and medium wave ultraviolet B (UVB). 

UVR is present during all daylight hours, found in many types of artificial lighting and even lightning. Unless patients with XP are protected from UVR, their skin and eyes will be severely damaged and this can lead to skin cancer. XP patients are at a 10,000 fold increased risk of developing skin cancer than the general population and often this starts at a very young age.

About 30% of people with XP also develop neurological abnormalities which can range from learning difficulties, hearing loss and eye sight problems to loss of gross motor skills and mobility. 

There is no cure for XP, but much can be done to prevent and treat some of the problems it causes.

Protection from all sources of UVR is required, including total daylight avoidance via specialised clothing and sunscreens. A significant commitment to lifestyle changes is also required to mitigate against the risk of exposure and combat its effects. People with XP must also undergo frequent skin, eye and neurological examinations and have prompt removal of cancerous tissue.


Visit the following link for details of the UK's national dedicated XP service based at Guys & St Thomas Hospital, London, UK; and for additional useful links and references.