Incontinentia pigmenti in Arizona Indians including transmission from mother to son inconsistent with the half chromatid mutation model.

Incontinentia pigmenti (IP) is an X-linked dominant disease, usually lethal to males. To explain occasional sporadic IP males, the half chromatid mutation model (Gartler & Francke 1975) has been invoked (Lenz 1975). We here report four cases of American Indians with IP. Two girls had sporadic IP. One affected boy's mother had IP. This is the first report of mother-to-son transmission of IP, indicating that a male with an inherited whole chromatid mutation for IP can escape lethality.