Cosegregation of X-linked retinitis pigmentosa and hemophilia A

We examined a family pedigree in which retinitis pigmentosa and hemophilia A were inherited in an X-linked manner. Six female carriers were identified by electroretinography. Results of ophthalmoscopic examination were normal in two women, while four displayed marked variability in phenotypic expression. Six of seven males identified with retinitis pigmentosa had hemophilia A. One asymptomatic boy had a markedly abnormal electroretinogram despite normal ophthalmoscopic examination. Pedigree analysis showed a high recombination rate, which would be expected as these two genes are known to be at opposite arms of the X chromosome.