sentences:  The lack of correlation between specific genetic mutations and observed phenotype, particularly with regard to sex reversal, give clear evidence of the variable expressivity of the disease.Milder forms of the disease, seen in those who live beyond the neonatal period and those with ACD, may be attributable to somatic mosaicism—particularly for those with mutations within the SOX9 coding region.Chromosomal aberrations in the upstream control regions or residual activity of the mutant SOX9 protein could also be responsible for the milder forms of the disease.