FIFTH INTERNATIONAL CONGRESS OF HUMAN GENETICS

We have ascertained 13 individuals in 4 sibships who exhibit a spectrum of clinical manifestations consisting of various forms of collagen vascular disease (CV), including discoid lupus, polymyositis, dermatomyositis and juvenile rheumatoid arthritis; mild spastic paraplegia with mild mental retardation (SP); and severe spastic quadriplegia with severe mental retardation (SQ), alone or in combination: CV (2); probable CV (2); CV + SP (4); SP (2); SQ (3). All 13 affected individuals are offspring of consanguineous marriages, and their parents can all be traced to a common ancestral couple of Acadian descent. The apparently random combination of manifestations might suggest that at least two autosomal recessive traits, those for CV and for SP/SQ, are segregating independently. However, linkage studies on 34 family members using 23 independent systems resulted in significant linkage with the Duffy locus (P<0.05) when all phenotypes were considered together. HL A typing in one sibship showed that all affected individuals inherited at least one W21 gene, again regardless of phenotype. Furthermore, all affected individuals and their parents had significantly elevated IgA levels. Thus, the possibility of a single mutant gene with pleiotropic effects, perhaps determining a common immunological defect responsible for both the collagen vascular and neurological manifestations, seems more likely.