Cystic fibrosis: Evidence for a genetic compound from a family study in cell culture.

Although the majority of patients with cystic fibrosis (CF) show a typical clinical course, a minority with the same clinical phenotype at the time of initial diagnosis have an atypical (mild) course. Skin fibroblast cultures were established from 49 members of the family of one such atypical CF adult patient, previously identified (Danes et al. 1976) as CF Class II (ametachromatic and no metabolic cooperation with CF Class I fibroblasts), the offspring of Class I (metachromatic, metabolic cooperation with normal fibroblasts)/Class II mating. The culture phenotype for Class I was traced on the maternal side and for Class II on the paternal side through consecutive generations and the culture phenotype of each class segregated. This family study added experimental evidence to support the hypothesis that the atypical (mild) clinical features and course of this adult CF patient were due to two different CF genes combining to produce a genetic compound expressing a mild form of CF.