CFTR and cystic fibrosis: The second family (Family B) was identified when individual II-I was diagnosed with CFTR-related metabolic syndrome (CRMS) based on elevated newborn immunoreactive trypsinogen (IRT), nondiagnostic sweat chloride values (< 60 mEq/L), and a CFTR genotype that includes variants not known to be definitively CF-causing (F312del and c.1736A>G [p.Asp579Gly; legacy: D579G]).