Letter: Cellular metachromasia with toluidine blue O in cultured white cells of cystic fibrosis heterozygotes.

We examined white cell cultures from 45 parents of CF patients (ie, 
compulsory heterozygotes) to confirm if possible the existence of an ametachromatic 
group (class III0 and the quantitate this class in relation to 
the numbers of heterozygotes showing vesicular cytoplasmic metachromasia (class I0 and 
generalized metachromasia (class II). Leucocyte cultures from the 45 CF carriers 
were set up in parallel with similar cultures from 45 normal 
healthy controls. The results confirm the value of the Toluidine Blue 
O metachromasia phenomenon in white cell cultures as a method for 
heterozygote detection in cystic fibrosis and suggest that it may be 
justified to replace the tedious, expensive and time-consuming fibroblast technique with 
the much simpler and more rapid leukocyte culture procedure. The simplicity 
and apparent reliability of the leukocyte culture procedure as outlined here 
should facilitate intrafamilial investigation and co-ordination of metachromasia class with other 
parameters such as sweat electrolytes, ciliary dyskinetic factor and clinical manifestations. 
Such a study, if it revealed distinct and consistent phenotypic correlations, 
might furnish valuable additional evidence for genetic heterogeneity in cystic fibrosis. 
