Genetic Heterogeneity Correlated with Phenotypic Variability in 48 Patients with Cystic Fibrosis

Background/Objectives: Cystic fibrosis (CF) is a rare autosomal recessive genetic disease that has a progressive and multisystemic course. The spectrum and frequency of mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) vary both in European countries and in other geographical regions. The aim of our retrospective study was to present the genetic variants identified in a group of 48 CF patients from the Moldova region (Romania), as well as to establish genotype–phenotype correlations. Methods: Genetic testing was initially performed for 38 CFTR mutations, and in heterozygous patients or those in whom no mutation was detected, CFTR gene sequencing (NGS) was performed. Results: The compound heterozygous genotype was identified in 26 (54.16%) of the patients (with one of the alleles being F508del), while 22 (45.83%) patients had the homozygous F508del genotype. The F508del variant was the most frequent (69.79%), followed by G542X (6.25%, 6/96). Several new variants were also identified that had not been reported in other studies from Romania (R1158X, K598*, R347H, c.2589_2599del, R496H, and CFTRdele2). Phenotypic manifestations in patients with CFTR class I, II, III and VII variants (homozygous and compound heterozygous) were more severe compared to those in patients with CFTR class IV, V and VI mutations, with the data obtained being consistent with those in the literature. Respiratory tract involvement was present in 77.08% of the patients, being more frequent in patients with the compound heterozygous genotype compared to the homozygous F508del genotype. Most patients had exocrine pancreatic insufficiency (EPI) (85.41%). Gastrointestinal manifestations included hepatocytolysis (66.66%) and biliary cirrhosis (0.41%). Meconium ileus was detected in 18.75% of patients, all with a compound heterozygous genotype. Conclusions: We compared the results obtained with data from the literature and correlated the detected CFTR variant (genotype) with the phenotypic manifestations, highlighting certain particularities present in some patients. Genetic testing allows for early diagnosis and adapted management, including personalized treatment for each patient. Identification of novel unclassified CFTR variants still remains a challenge for clinicians. NGS-based screening of heterozygous healthy carriers is important for both genetic counseling and prenatal diagnosis.