Xeroderma Pigmentosum, also known as XP, is a condition thatis characterized by an extreme sensitivity to ultraviolet rays. This disease normally affects the parts ofthe body that are exposed to sunlight, however, some individuals also face issueswith their nervous systems. XP is a rare disorder and affects an estimated onein a million people across the United States and Europe (U.S. National Libraryof Medicine, 2010.) Xeroderma Pigmentosum is an autosomal recessively inheriteddisease, which means an individual can only be affected if both of theirparents are carriers for the disorder (Swanson, 2017.
) Every cellin a healthy human being contains two copies of each gene; one inherited fromthe mother, the other from the father. Since Xeroderma Pigmentosum follows anautosomal recessive inheritance pattern, the mutation must be present in bothcopies in order for the offspring to be affected. An individual who only has onecopy of their genes with the mutation is considered a carrier. When bothparents are carriers of a recessive mutation on the same gene, their childrenhave a 25% chance of inheriting two mutated copies of the gene. XerodermaPigmentosum is caused by mutations to genes that are involved in repairingdamaged deoxyribose nucleic acid, DNA. There are at least eight genes that areknown to play a role in XP. Many of the cases studied in the United States haveresulted from mutations in the XPC, ERCC2, or POLH genes (U.
S. National Libraryof Medicine, 2010.) Mutations in the other genes affect an even smallerpopulation of individuals effected. Variations to these genes alters the body’sability to repair skin cells that have been exposed to any ultraviolet rays.Normal cells have the ability to fix DNA exposed to the UV rays, before anydamage is done. In people with XP, with more exposure comes more abnormalitiesin their skin cells. This is what causes the cells to become cancerous andeventually die.
It is vital that individuals with this disorder are diagnosedas early as possible, in order to take important precautions in their everydaylives. Prior tochildbirth, there is a variety of different tests that can be done to helpdiagnose any conditions that the baby has. Amniocentesis, Chorionic villoussampling, and cultures of amniotic cells are a few of the tests done to examinethe child’s DNA, prior to birth (Swanson, 2017.
) If parents do not have genetictesting done on their offspring, they can expect to see signs and symptoms ofXeroderma Pigmentosum through infancy and early childhood. In most instances,by age two, almost all children affected by the disorder develop freckling ofthe skin in the areas most often exposed to the sun, such as the hands and face(Lin, Tamura, & Kraemer, 2017.) Sometimes it is not the freckling thatsuggests XP, instead sudden loss of hearing could be a signaling factor. Around25% of individuals with XP also develop abnormalities of the nervous system andcan suffer from progressive neuro-degeneration with hearing loss. CameronBricker was born with Xeroderma Pigmentosum and her parents and doctors did notconsider XP as a diagnosis until she suddenly lost her hearing at the age offive (CheckOrphanORG, 2014.) Bricker’s sudden loss of hearing also suggestedthat she may have De Sanctis-Cacchione syndrome, which is often associated withXeroderma Pigmentosum. De Sanctis-Cacchione is another extremely rare disorder thateffects the nervous system in those affected by XP. Mental retardation, dwarfism,underdevelopment of sex characteristics, abnormally small head, ataxia, andhyporeflexia, are the most common abnormalities that can occur as a result ofthis condition (National Organization for Rare Disorders (NORD), 2003.
) Aside fromthe possible neurological defects, the main issue with Xeroderma Pigmentosum isthe skin conditions that develop for individuals with the disease. Since thedamage done to the genetic material is irreversible, it is important for thoseeffected by XP, to avoid exposure to UV rays. Some individuals can suffer frompainful symptoms after only ten minutes of sun exposure.
These people cansuffer from sunburn that never heals, painful blistering, spider-like bloodvessels, patches of discolored skin, crusting and scaling of the skin, andvarious types of skin cancers (Swanson, 2017.) The risk of developing skincancer is much greater in individuals who suffer from XP. In fact, the risk of developingnon-melanoma skin cancers, such as basal cell carcinoma or squamous cellcarcinoma, is almost 10,000 times greater and the risk of developing melanoma relatedskin cancers is around 2,000 times greater (Lin, Tamura, & Kraemer, 2017.) Theonset of these cancers can vary from one person to the next and the amount ofsun exposure that they’ve encountered also plays a huge role in the developmentof it as well. Another symptom associate with Xeroderma Pigmentosum that varieswith the amount of sun exposure one experiences is lentigos. Lentigos are apatchy freckling on the skin that can occur in people with or without XP. Forpeople with Xeroderma Pigmentosum, these skin spots can occur on the face andhands in the first two years of life.
Although they normally appear on theparts of the body that have the most sun exposure, they can appear anywhere onthe body. Normal, healthy individuals on the other hand can see these lentigosappear after prolonged sun exposure later on in life (Lin, Tamura, &Kraemer, 2017.)