Letter: Protein level in the meconium of a homozygotic and a heterozygotic infant with cystic fibrosis.

In our patient, the second child of a married couple heterozygous for 
cystic fibrosis , the meconium protein content was higher than that 
of controls. He has no symptoms of cystic fibrosis. The determination 
of sodium and chloride ions in the sweat excluded homozygosity; the 
bromide test led us to conclude the child to be a 
heterozygote. In our patient the protein content of the meconium, the 
majority of which was albumin, was two- to threefold that of 
the controls. This elevated protein content, however, was not characteristic of 
homozygosity. Our results lead us to conclude that a high protein 
content of meconium does not unconditionally indicate the homozygotic state for 
cystic fibrosis. It would appear that heterozygosity for cystic fibrosis is 
not completely without abnormality. Our findings perhaps explain "false positive" results 
recorded in the literature. High-protein content in the meconium may be 
useful in the identification of heterozygotes too. 