Reaching the diagnosis of cystic fibrosis - The limits of the spectrum

Background: Cystic fibrosis is the most common life-limiting autosomal recessive genetic disorder in Caucasians. Typically it is a multisystem disease diagnosed by increased chloride levels on sweat testing, with mortality due mainly to progressive respiratory disease. The clinical spectrum of CF has recently been much expanded. Genetic testing for mutant CF transmembrane regulator has revealed atypical cases where sweat test results are borderline or normal. In other patients, genetic mutations cannot be identified but abnormal CFTR function is shown using nasal potential difference measurement. Objectives: To highlight the diagnostic and therapeutic dilemmas in cases of atypical cystic fibrosis. Methods: We reviewed patients with atypical CF and widely varying phenotype who are managed at Schneider Children's Medical Center of Israel. Results: Two patients had severe lung disease but little expression in other organs. Accurate diagnosis was essential to enable aggressive therapy in a specialized center. Four other patients are in excellent general health but have symptoms limited to male infertility, heat exhaustion, pancreatitis or transient liver dysfunction, while lung disease is minimal. For these patients, careful counseling is needed to avoid unnecessary upheaval, inappropriately aggressive management, and the psychosocial implications of a CF diagnosis. These dilemmas have increased considerably in our center, as in others worldwide. Conclusion: It is our obligation as clinicians - at the level of both primary physician and referral center - to maintain an ever higher index of suspicion for CF, tempered by a rational rpogram of counseling and management appropriate to the individual.