The disorder was suspected at the age of 9 months based on the typical clinical signs, respiratory manifestations, intestinal syndrome and pseudo-Bartter syndrome that developed at this age, and confirmed by positive sweat tests (sweat conductivity values in the brothers were 127 mmol/L and 118 mmol/L) and molecular genetic testing (search for common CFTR gene mutations): the genotype F508del/CFTRdele2.3 (Del21kb) was determined. This evidence concerns the gene CFTR and Bartter syndrome.