Definition of Incontinentia pigmenti

Incontinentia pigmenti: A genetic disease that begins soon after birth with the development of blisters on the trunk and limbs. These blisters then heal, but leave dark hyperpigmented streaks and marble-like whorls on the skin. Other key features include dental and nail abnormalities, bald patches and, in about one-third of cases, mental retardation.

Incontinentia pigmenti (IP) is inherited as an X-linked dominant trait. The gene for IP is called IKBKG. A girl with IP has inherited the IKBKG mutation from a parent or has a new IKBKG mutation. IP is lethal in most, but not all, males. Mothers with IP have an equal chance of having a normal son, a normal daughter, and an IP daughter.

Females with IP have nonrandom X-chromosome inactivation. Normally, one X chromosome in each cell of a female is randomly inactivated. In females with certain X-linked conditions, including IP, the X chromosome with the mutant allele is preferentially inactivated. This phenomenon is termed non-random (or skewed) X-chromosome inactivation.

IP is also known as Bloch-Sulzberger syndrome.