Clinical variations of cystic fibrosis.

It is estimated that cystic fibrosis affects approximately one of every 2,000 
white children born in the United States, and is now generally 
regarded as the commonest serious metabolic disorder of white children with 
the exception of diabetes mellitus. Its occurrence in children of Afro-Americans 
is quite rare and exceedingly so in those of Oriental extraction. 
Since cystic fibrosis is genetically determined as an autosomal recessive trait, 
and since the obligate heterozygote parent is entirely asymptomatic, the disease 
on its first occurrence in a given family can only be 
suspected by its manifestations in the patient himself. At present there 
is no test available for the detection of cystic fibrosis which 
can be applied as a simple, practical screening test, such as 
is available for phenylketonuria. Diagnostic tests are, therefore, used to confirm 
or refute the diagnosis of cystic fibrosis when suggestive symptoms arise 
or when a sibling or relative is known to have the 
disease. 