Copyright © 2017 American Academy of Pediatrics. From: Pertussis (Whooping Cough) Red Book® 2015, 2015 Figure Legend: String sign of infantile hypertrophic pyloric stenosis. An association with oral erythromycin has been reported in infants younger than 3 weeks with infantile hypertrophic pyloric stenosis. This is a potential complication, though not a contraindication, when treating young infants with erythromycin for pertussis or other conditions. Courtesy of Edgar O. Ledbetter, MD, FAAP Date of download: 11/14/2017 Copyright © 2017 American Academy of Pediatrics. All rights reserved.