The Q359K/T360K mutation causes cystic fibrosis in Georgian Jews

Abstract Background The Q359K/T360K mutation, described in Jewish CF patients of Georgian decent, is of questionable clinical significance. Methods Clinical records of patients with the Q359K/T360K mutation from three CF centers were studied for phenotypic expression and putative mechanism of dysfunction. Computer models of mutant CFTR were constructed. Results Nine patients (4 homozygous) of Georgian Jewish origin were included. Age at diagnosis was 9.4 (0.25–38.2) years, median (range). Sweat chloride was 106 ± 13 meq/L, mean ± SD. Nasal Potential Difference performed in three, was abnormal. All had pulmonary symptoms since early childhood and bronchiectasis. Median FEV 1 was 88 (40–121)%. Five had chronic mucoid P. aeruginosa . Homozygous patients were pancreatic insufficient. Enzyme supplementation was initiated at 3.8 (1–14.7) years, median (range). Structural models hint at possible interference of this mutation with transmembrane chloride transport. Conclusion In our cohort, the Q359K/T360K mutation resulted in a severe CF phenotype, although with residual early CFTR function. The CFTR2 database should consider defining this mutation as CF-causing.