EVIDENCE OF GENETIC AND PHENOTYPIC HETEROGENEITY IN THE ROMANO-WARD SYNDROME

We report two families with phenotypically different forms of Romano-W ard syndrome. In one family, only five of 18 affected subjects are sym ptomatic, whereas in the other the proportion is three out of five. Th e families show distinct ECG morphologies, in addition to QT prolongat ion. Previous reports have shown genetic linkage either to the HLA loc us on chromosome 6 or the Harvey-ras oncogene on, chromosome 11. No li nkage was found to either locus in the families reported here. The imp lications of phenotypic and genotypic heterogeneity in Romano-Ward syn drome are discussed in relation to the neurogenic and intrinsic models of pathogenesis.