X-linked ichthyosis
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| X-linked ichthyosis Classification and external resources |
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| ICD-10 | Q80.1 |
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| ICD-9 | 757.1 |
| OMIM | 308100 |
| DiseasesDB | 29136 |
| eMedicine | derm/191 |
| MeSH | D016114 |
X-linked icthyosis is a skin condition due to the hereditary deficiency of an enzyme called steroid sulfatase. This enzyme is found throughout the body but seems to be most important in the skin. When there is not enough of this enzyme in the skin, it cannot "shed" properly and so the skin appears dry and scaly, appearing darker and cracked.
Prenatally, the condition affects placental oestrogen production, as precursor steroids from the male fetus are not fully utilized due to difficulty in removing their sulfate group. Estriol levels during pregnancy are low. Pregnancies may be complicated by an inability to go into spontaneous labor.
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[edit] Genetics
This condition results from the lack of the gene that codes for steroid sulfatase. When present, this gene is located on the distal short arm of the X chromosome. Because the gene is located on the X chromosome, this condition most commonly affects males.
In chromosomal group 24 there are two possible different chromosomes that can be present: an X chromosome and a Y chromosome. Females have two X chromosomes and males have one X and one Y chromosome. Because there is only one X chromosome in a male, if the gene is missing, then there will be no genes coding for the production of the enzyme. In a female with the gene there will still be another X chromosome with the gene for the enzyme meaning that the body will still produce it. There is no way for a male to carry the disease without suffering because he has only one X chromosome.
Females can carry the disease, but they can also be sufferers too, if both the girl's father and mother are missing the gene. This is however extremely rare and over 95% of the cases seen are males.[citation needed]
This chromosome with the faulty or missing gene can get passed on to subsequent generations: An affected male could have a daughter, who will have two X chromosomes, one of which must have come from the father giving her the faulty gene. Assuming the mother has a normal X chromosome, the daughter will not suffer from it as she still has the correct gene for steroid sulfatase on the maternal X chromosome. The daughter becomes a genetic carrier but does not suffer from the condition herself.
If an affected male has a boy with a woman who does not carry the genetic defect, then the boy will not be either a sufferer or a carrier of the gene because the boy always has the Y chromosome from his father and the X chromosome from his mother. If she passes along a normal X chromosome, then the boy will be completely clear of the faulty genes.
[edit] Diagnosis
Diagnosis before birth is possible using a genetic test. It is illegal in some countries to take cell samples from a foetus unless there are very important medical reasons to do so. There are very few associated conditions, all of which are rarer and so it is probably not necessary to test for even if the mother knows she is a carrier. Symptoms can take varying amounts of time to become evident, from a few hours after birth, up to a year in milder cases where the gene is just damaged rather than being not present. Diagnosis usually comes from a dermatologist since the condition is rare, and they will also form a care plan.
[edit] Treatment
There is no cure because the condition is genetic, research into this is being funded by the Icthyosis Support Group - http://www.ichthyosis.org.uk. Smoothing the skin and relieving the symptoms is achieved using prescribed moisturising creams, often containing Urea or Lactate (lactic acid). 'Unguentum M' is popular. Bath lotions can be easier to use than creams, as they don't have to be applied by hand and are not as greasy. Shampoos, like Ceanel concentrate, for the dry scalp which otherwise presents itself as extremely severe dandruff.
The most effective creams are greasier so experimentation is required to find the right balance between ease of application and effectiveness. Creams that are very effective.
There are reports that the skin condition gets less severe with age, but this hasn't been scientifically tested as yet.
[edit] Associated Medical Problems
Associated Medical Problems are extremely rare and do not affect most people with this condition.
Sometimes when the gene for production of steroid sulphatase gets mutated it can "knock out" other neighbouring genes. On one side are genes that if affected could cause mild retardation and short stature...therefore if a boy has this he will not only have dry skin, but also be short and have learning difficulties. On the other side is a gene known as the 'Kallmann's gene' which if it is missing or damaged may affect normal puberty and Hormone replacement tablets can be given to correct this. There could also be other problems with Kallmann;s gene missing such as subtle problems with hand movements, the ability to smell,and kidney function may not be optimal. This is known as Kallmann's syndrome. Unfortunately most doctors are not aware of these associated problems and so you may need to fight to get the appropriate help and treatment. Carriers of X-linked Icthyosis (who can only be women) will not experience any of these problems but rarely can have problems giving birth as the placenta makes steroid sulphatase and there are associations between this and normal labour. For this reason carriers should ensure their obstetrician is aware of the condition.
[edit] See also
[edit] References
- Jöbsis AC, De Groot WP, Tigges AJ, et al (1980). "X-linked ichthyosis and X-linked placental sulfatase deficiency: a disease entity. Histochemical observations". Am. J. Pathol. 99 (2): 279-89. PMID 6929654.
