Reassessment of the specificity of lens opacities in myotonic dystrophy

Cataract has been considered for a long time one of the major indicators of the presence of the mutated myotonic dystrophy (DM) gene in asymptomatic relatives of DM patients. However, some recent studies show that not all cases of cataract typical of DM are associated with the disease even in members of DM families. In order to determine the frequency of lens opacities characteristic of DM in the general population and to evaluate the specificity of lens anomalies for detection of the DM premutation, we screened a sample of 1,400 random individuals for the presence of 'myotonic cataract'. Ten individuals were found with the typical lens opacities and no neuromuscular signs of DM; molecular analysis of the DM mutation showed that they all carried two normal alleles. Our data allow to conclude that bilateral cortical iridescent and posterior cortical lens opacities cannot be considered a marker of the presence of the DM premutation in the general population.