a genetic disease with blisters that develop soon after birth on the trunk and limbs, then heal, but leave dark (hyperpigmented) streaks and marble-like whorls on the skin. (the name came from the erroneous idea that the skin cells were incontinent of pigment and could not contain it normally.) other key features of ip include dental and nail abnormalities, bald patches, and (in about 1/3rd of cases) mental retardation. Ip is an x-linked dominant with male lethality. The ip gene is in band q28 on the x chromosome. Mothers with ip have an equal chance of having a normal or ip daughter or a normal son. The ip sons die before birth. Ip is also known as bloch-sulzberger syndrome.