Medical Genetics

X-linked Dominant: Incontinentia Pigmenti

Genes are inherited from our biological parents in specific ways. One of the basic patterns of inheritance of our genes is called X-linked dominant inheritance.

What is X-linked dominant inheritance?

X-linked dominant inheritance is where the gene is located on the X chromosome, but the gene acts in a dominant manner. This means that both males and females can display the trait or disorder, by only having one copy of the gene.

Depending on the disorder, often times a gene that is X-linked dominant causes a male pregnancy not to survive. Another way scientists and physicians refer to this process is to say that "there is lethality in males." This means that the gene is passed from mother to daughter, and, if passed to a son, the pregnancy miscarries. Only those sons without the gene survive to be born and are born healthy. One example of an X-linked dominant condition is called incontinentia pigmenti (IP).

What is incontinentia pigmenti (IP)?

IP is extremely rare. The main features occur in the skin where a blistering rash occurs in the newborn period, followed by the blisters becoming raised-like warts. Next, brown swirls appear in the skin, followed by the appearance of light swirls. The result is a "marble cake-like" appearance on the skin. Other health problems can be seen in IP involving the eyes, central nervous system, teeth, nails, and hair. The severity varies from person to person.