What is Xeroderma Pigmentosum?
Xeroderma pigmentosum commonly known as XP is an autosomal recessive disorder involving the DNA repair. It is a genetic disorder characterized by extreme sensitivity towards the ultraviolet radiation or the ultraviolet rays of the sun. This condition greatly affects the areas of the skin that are in constant exposure to the sun including the eyes.
Xeroderma pigmentosum is a rare hereditary skin condition which is at high risk for developing into skin cancer. Individuals suffering from this condition are extremely advise against staying under the sunlight as their DNA repair has the inability to repair the damages caused by ultraviolet rays from the sunlight. Children suffering from this disorder are often referred to as Children of the night as they are not allowed to be exposed under the sunlight even in very small amount UV rays.
Xeroderma pigmentosum affects both male and female equally and without racial predilection. It can affect people globally and is usually recognized on the first to second year of life. Morbidity is linked with the development of metastatic malignant melanoma and squamous cell carcinoma which are both potential in xeroderma pigmentosum. Both the squamous and basal skin cancer and melanoma usually develop to patient at a very young age or about the age of 10 years and below and children with xeroderma pigmentosum are also at high risk for developing multiple skin cancer all throughout their lives.
In xeroderma pigmentosum, the skin or the areas of the skin in constant exposure to the sun including the eyes are affected. Neurologic deficit is also expected in children suffering from this disorder.
The symptoms of the skin in xeroderma pigmentosum basically go through three stages and such are:
1st stage usually occurs during the 6th month of life where the skin is characterized by scaling, diffuse erythema and increased pigmentation that appears similar to a freckle. Children with xeroderma pigmentosum have normal or healthy skin at the time of birth until the skin changes or until the 6th month of their lives.
2nd stage is characterized by the development of telangiectasia, hyperpigmentation and atrophy of the skin. The changes in the skin make it similar to the appearance of skin in chronic radiodermatitis. Telangiectasia not only appears on the areas of the skin that are exposed to the sun but also develops in unexposed areas including the buccal mucosa.
3rd stage is described with the development of multiple malignancies as well as with the development of basal cell carcinoma, squamous cell carcinoma, fibrosarcoma and malignant melanoma.
The common skin symptoms of xeroderma include the following:
- Photosensitivity is prevalent in 50% of patients where severe sensitivity under the ultraviolet rays often leads to sunburn even with small amount of exposure
- Skin tanning and formation of freckles or hyperpigmentation in the absence of sunburn also occurs in patients without sensitivity to sunlight
- Dry skin is common including a scaly skin and blood vessels resembling a spider
- Skin cancer develops at the age of 10 years and below especially to those who do not use sunscreen and other protection when exposing under the sun
The eye symptoms in xeroderma pigmentosum include the following:
- High sensitivity to sunlight which makes the eyes painful
- Inflammation of the conjunctiva
- Inflammation of the cornea which in severe case can cause opification and vascularisation of the cornea
- Growth of benign or malignant tumor in the conjunctiva and eyelids
- Ectropion or entropion of the edge of the eyelids
- Falling off of the eyelashes and darkening of the skin surrounding the eyes or the eyelids
Neurologic problems also occur in patients with xeroderma pigmentosum which is relative to the sensitivity against ultraviolet radiation. The neurological problems may be mild or severe and the symptoms include the following:
- Head that is smaller in size than the average size or the condition known as microcephaly
- There may be a delay in sexual development and the condition known as dwarfism
- Intellectual impairment which is progressive or may get worse overtime
- Episode of seizures
- Xeroderma pigmentosum associated with neurologic abnormalities such as mental retardation and is termed as De Sanctis-Cacchione syndrome
Xeroderma pigmentosum is a genetic condition in an autosomal recessive pattern. It can be passed on from one offspring to another in a family with the history of the disorder. In order for the disorder to be inherited, both parents should be a carrier of the defective gene.
Xeroderma pigmentosum is the result of mutation or alteration in Nucleotide excision repair enzymes. The alteration in the gene causes the inability to repair the damaged DNA caused by toxic chemicals. The alterations in the NER results to the dysfunction of the DNA repair in carrying out its function of identifying DNA damage, snipping out the anomalous area and restoring with the right DNA.
Xeroderma pigmentosum has no known cure or treatment. The focus of management is geared towards the problem presented as a result of deficiencies brought by the disorder. Prevention of future problems is included in the management of xeroderma pigmentosum.
Ultraviolet radiation is the primary nemesis of xeroderma pigmentosum that avoidance of the ultraviolet light is necessary. The avoidance of UV rays improves the prognosis for patient suffering from the disorder. Certain practices or methods are needed to be done in order to realize an improved prognosis and such include the following:
- Prohibiting outdoor activities during the day
- Application of sunscreen and other protection from the UV rays if daylight outdoor activities cannot be avoided
- Wearing of protective gears and clothing to cover from sunlight
- Installation of protective films on the windows to filter out UV rays
Xeroderma pigmentosum is a rare genetic disorder that generally does not have a good prognosis. Only few patients survive beyond the age of 20. Patients with a mild form of xeroderma pigmentosum survive until the age of years.
The mortality of xeroderma pigmentosum is related to the development of malignant melanoma and squamous cell carcinoma. Skin cancer is highly potential in children of XP that by the time they reach the age of 8 to 10 years, multiple skin cancer develops especially to those who do not have ample protection against the UV radiation.