Hypertrophic pyloric stenosis in infants following pertussis prophylaxis with erythromycin--Knoxville, Tennessee, 1999.

In February 1999, pertussis was diagnosed in six neonates born at hospital A in Knoxville, Tennessee. Because a health-care worker at hospital A was most likely the source of exposure, the local health department recommended on February 25, 1999, that erythromycin be prescribed as postexposure prophylaxis for the approximately 200 infants born at hospital A during February 1-24, 1999. In March 1999, local pediatric surgeons noticed an increased number of cases of infantile hypertrophic pyloric stenosis (IHPS) in the area, with seven cases occurring during a 2-week period. All seven IHPS cases were in infants born in hospital A during February who were given erythromycin orally for prophylaxis following possible exposure to pertussis, although none had pertussis diagnosed. The Tennessee Department of Health and CDC investigated the cluster of IHPS cases and its possible association with use of erythromycin. This report summarizes the results of the investigation, which suggest a causal role of erythromycin in this cluster of IHPS cases.