Despite generalnutritional improvements in CF care, still growth retardation,58,59 delayedpuberty,59,60 and disturbed body composition59,61 are reported, and all couldcontribute to underdevelopment of the neuromuscular skills and consecutively CRF.Sweat chloride concentration was not related to CRF levels in our sample, and isalso consistent with earlier findings that CFTR genotype was not associated with CRF.13 The gene discussed is CFTR; the disease is cystic fibrosis.