Description
Labels Xeroderma Pigmentosum
Xeroderma pigmentosum is a rare skin disorder caused by mutations in
any of eight different genes that govern the ability of skin cells to repair
damage to DNA (the genetic material inside a cell) caused by exposure
to sunlight. In a normal person, exposure to the ultraviolet radiation in
sunlight causes damage to the DNA of the cells in the upper layer of the
skin. This damage is fixed by a mechanism known as nucleotide excision
repair, or NER. In patients with XP, however, the enzymes that carry out
NER are either reduced in effectiveness or missing entirely. When the
damage to the cell’s DNA cannot be repaired, the DNA itself may
mutate, leading to the death of skin cells or to skin cancer. The average
child with XP develops the first signs of skin cancer around age eight.
Xeroderma pigmentosa progresses in three stages:
About 80 percent of patients with XP develop eye problems related
to sun exposure. The eyes may become bloodshot and painfully
sensitive to light. Both cancerous and noncancerous growths may
appear near the eyes. In a few cases the eyelids may shrink or
even disappear entirely.
Between 20 and 30 percent of patients with XP develop symptoms
affecting the nervous system in late childhood or early adolescence.
These symptoms range from the loss of tendon reflexes and poor
coordination to hearing loss and mental retardation. The child’s
growth may also slow down. These neurologic symptoms
tend to get worse over time.
any of eight different genes that govern the ability of skin cells to repair
damage to DNA (the genetic material inside a cell) caused by exposure
to sunlight. In a normal person, exposure to the ultraviolet radiation in
sunlight causes damage to the DNA of the cells in the upper layer of the
skin. This damage is fixed by a mechanism known as nucleotide excision
repair, or NER. In patients with XP, however, the enzymes that carry out
NER are either reduced in effectiveness or missing entirely. When the
damage to the cell’s DNA cannot be repaired, the DNA itself may
mutate, leading to the death of skin cells or to skin cancer. The average
child with XP develops the first signs of skin cancer around age eight.
Xeroderma pigmentosa progresses in three stages:
- Stage 1. The child’s skin is healthy at birth but around six months
of age the skin develops reddish, scaly patches with heavy freckling
or sunburn after even short exposure to sunlight. At first only the
face and other areas exposed to direct sun are affected, but gradually
the skin changesappear on the neck, lower legs, and even the chest. - Stage 2. The skin develops irregular patches of lightened or
darkened skin with spidery patterns of blood vessels appearing
underneath. The skin also becomes much thinner. - Stage 3. This stage begins when the child is four to five years old.
Skin cancers and scaly patches known as solar keratoses appear.
About 80 percent of patients with XP develop eye problems related
to sun exposure. The eyes may become bloodshot and painfully
sensitive to light. Both cancerous and noncancerous growths may
appear near the eyes. In a few cases the eyelids may shrink or
even disappear entirely.
Between 20 and 30 percent of patients with XP develop symptoms
affecting the nervous system in late childhood or early adolescence.
These symptoms range from the loss of tendon reflexes and poor
coordination to hearing loss and mental retardation. The child’s
growth may also slow down. These neurologic symptoms
tend to get worse over time.
0 Response to "Description"
Post a Comment