OPITZ GBBB SYNDROME - CHROMOSOMAL EVIDENCE OF AN X-LINKED FORM

BBB syndrome and G syndrome were originally reported as distinct X-lin ked disorders. Clinical studies indicated that BBB and G syndromes wer e likely to represent variant expression of the same disorder, now ref erred to as ''Opitz'' GBBB syndrome. Several occurrences of male-to-ma le transmission in both syndromes led to the hypothesis that GBBB synd rome was a single autosomal dominant, sex influenced disorder, now ten tatively mapped to 5p12-13. We report on a large pedigree in which GBB B syndrome appears to cosegregate with a pericentric inversion of the X chromosome inv(X)(p22.3q26). It indicates the possible existence of a true X-linked form of GBBB syndrome, which does not appear phenotypi cally different from its autosomal counterpart. The gene could map in the vicinity of the breakpoints, in Xp or Xq. The existence of two gen es affecting a common pathogenetic pathway could explain the gender-de pendent expressivity of GBBB phenotype. (C) 1995 Wiley-Liss, Inc.