Manifestations of cystic fibrosis in adults [letter].

Cystic fibrosis (CF) is a recessive autosomal genetic disease in which exocrine 
glands secrete highly viscous mucus. Variable genetic penetrance ("organ sparing") results 
in a broad spectrum of clinical presentations. The diagnosis of CF 
is usually established by the presence of chronic obstructive lung disease 
and/or gastrointestinal dysfunction, together with elevated levels of sweat electrolytes (chloride 
> 60 mEq/liter), markedly diminished duodenal pancreatic enzyme concentrations, or pathologic 
changes in tissue. Family history may occasionally be helpful. The metabolic 
basis of CF is unknown. The classic stereotype of the CF 
patient is an infant with a chronic cough, diarrhea, and growth 
failure. Improved medical care is enabling many of these patients to 
reach adulthood, and increased diagnostic suspicion is resulting in identification of 
the disease in more adults. Based upon analysis of over 11,000 
cases of CF reported during the year 1974 by 119 Cystic 
Fibrosis Centers, the National Cystic Fibrosis Foundation estimated that the probability 
of an individual with CF surviving to age 20 was approximately 
39%. Although most of these adults are currently under the care 
of pediatricians, the development of medical, psychiatric, surgical, or obstetric complications 
may necessitate the involvement of other professionals. A joint study of 
cystic fibrosis in adults conducted by Duke Medical Center and the 
NIH has shown that the majority of affected adults, including those 
diagnosed early in life, are married and work full- or part-time. 
Many manifest few if any symptoms until relatively late in life. 
Since this study was retrospective, the reported frequencies of the clinical 
findings tend to underestimate, in all instances, the actual incidence in 
the population studied. The reported incidence of CF in the United 
States has been conservatively estimated at 1:2,000 live births. If all 
adults with clubbing, infertility, and other symptoms were evaluated for CF, 
the true incidence would certainly be higher. 