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To the Editor.
—In our article "Retinal Vascular Changes of Incontinentia Pigmenti" (Archives 94:743-746, 1976), it is stated that the condition is "probably autosomal dominant, but is lethal for boys, so most observed cases will be found in girls."Incontinentia pigmenti is now considered to be an X-linked dominant disorder. Male subjects are hemizygous, ie, they have only one of any of the genes found on the X chromosome. Thus, in the male subject, a mutant X chromosomal gene that codes for a structural protein (hence a dominant gene) would be the equivalent of a homozygous autosomal dominant mutation that is usually lethal or sublethal. It is thought that male fetuses with incontinentia pigmenti are usually spontaneously aborted, which is why this is almost exclusively a disease of female subjects.
Watzke RC. Incontinentia Pigmenti. Arch Ophthalmol. 1978;96(10):1922. doi:10.1001/archopht.1978.03910060408027