Four infants, 1 to 4 months of age, with cystic fibrosis, had severe bleeding caused by vitamin K deficiency and hypoprothrombinemia. The decreased prothrombin activity was attributed to poor dietary intake, malabsorption caused by pancreatic disease, and decreased synthesis following the administration of antibiotics. Second stage coagulation defects can be responsible for the presenting symptom of cystic fibrosis in early infancy. In infants with unexplained prolongation of the prothrombin time, the possibiliity of cystic fibrosis should be evaluated. Supplemental vitamin K should be administered to infants with cystic fibrosis.
Walters TR, Koch CHF. Hemorrhagic Diathesis and Cystic Fibrosis in Infancy. Am J Dis Child. 1972;124(5):641-642. doi:10.1001/archpedi.1972.02110170019002