The genotype of a new linked DNA marker, MP6d-9, is related to the clinical course of cystic fibrosis.

The clinical symptoms of a cohort of cystic fibrosis patients were related to their genotypes using RFLPs shown with MspI and the closely linked DNA marker MP6d-9. In the majority of CF chromosomes, the restriction site for MspI was present, and the genotype 2/2 was found most often in patients who were severely affected by the disease. The genotype 1/2 was significantly over-represented in patients with very mild clinical manifestations, including pancreatic sufficiency, absence of meconium ileus, and absence of Pseudomonas colonisation. When pancreatic dysfunction was present, the 1/2 genotype was associated with a mild form, while the 2/2 genotype was found in patients with severe insufficiency. None of our patients had the 1/1 genotype. These results indicate that the newly isolated MP6d-9 marker correlates with some important symptoms of cystic fibrosis.