As a paradigmatic example of the importance of reverse phenotyping to properly classify complex diseases resulting from multiple molecular diagnoses, we describe a 20-year-old woman affected with a syndromic intellectual disability disorder characterized by facial dysmorphism, scoliosis, peculiar behavior, short hands and feet associated with bronchiectasis, recurrence of pneumonia, P. aeruginosa infections, cholelithiasis and severe chronic constipation, who had a de novo pathogenic variant in USP7 and was compound heterozygous for pathogenic CFTR alleles. The gene discussed is CFTR; the disease is Chronic constipation.