Carrier detection in X-linked retinitis pigmentosa by multipoint DNA analysis. Problems due to genetic heterogeneity

DNA diagnosis of X-linked retinitis pigmentosa (XLRP) is hampered by its genetic heterogeneity, while a clinical subdivision is almost impossible to make. So far, diagnostic services have been offered only to those families in which linkage to one RP locus (RP2 or RP3) has been clearly established. In most families, however, the nature of the XLRP type cannot be distinguished on the basis of linkage analysis. Here the authors describe that in some families DNA diagnosis is nonetheless feasible, when polymorphic DNA markers are used which span the entire Xp21.1-Xcen region and when no recombination between these markers disturbs the phase.