LAUSR

INTRODUCTION Cystic fibrosis (CF) is a potentially severe disease. The development of new therapies with cystic fibrosis transmembrane conductance regulator (CFTR) modulators has been a great advance in the management of this condition because they improve the function of the faulty CFTR protein rather than palliate its consequences. CFTR modulator therapy improves pancreatic and lung function and, therefore, quality of life, with greater benefits the sooner treatment is started. For this reason, the use of these therapies is being approved for increasingly younger patients. Only two cases of pregnant women taking CFTR modulators therapy with CF fetuses have been reported, suggesting that it could resolve meconium ileus (MI) prenatally, and delay/prevent other consequences of CF. CASE PRESENTATION We report a case of a healthy pregnant patient who underwent CFTR modulator therapy with elexacaftor-tezacaftor-ivacaftor (ETI) in order to treat her fetus with CF (F508del homozygous CFTR mutation) and MI. Ultrasound findings suggestive of MI were observed at 24 weeks. Both parents were tested for CFTR mutations, and both were carriers of the F508del CFTR mutation. The fetus was diagnosed with CF by amniocentesis at 26+2 weeks. Maternal ETI therapy was initiated at 31+1 weeks and no dilated bowel was observed at 39 weeks. There were no signs of bowel obstruction after birth. Maternal ETI treatment was continued during breastfeeding, with normal liver function. Immunoreactive trypsinogen in the newborn was 58.1 ng/mL, sweat chloride test was 80 mmol/l, and fecal elastase on the second day of life was 58 μg/g. DISCUSSION/CONCLUSION Prenatal ETI treatment, as well as during breastfeeding, could solve, prevent and/or delay CF complications.