No Infantile Hypertrophic Pyloric Stenosis among Neonates who Received Erythromycin for Postexposure Prophylaxis against Pertussis

INTRODUCTION Pertussis, commonly known as whooping cough, is an infection caused by the bacterium Bordetella pertussis. This highly communicable disease, which affects susceptible individuals of any age, is spread by respiratory droplets and contact with recently contaminated objects. Bordetella pertussis causes inflammation of the larynx, trachea, and bronchi. Among neonates, the symptoms include life-threatening coughing and choking spells followed by apnea, cyanosis, bradycardia, and unresponsiveness; in this age group, the complications include pneumonia, seizures, intracranial hemorrhage, encephalopathy, and death.1 Among children and adults, the disease is characterized by paroxysmal staccato coughing with inspiratory whoop.1 Adults may also present atypically with prolonged repetitive cough without the inspiratory whoop; as such, pertussis may be underdiagnosed. 2 Childhood vaccinations against pertussis do not confer lifelong immunity, and people who were vaccinated as children may become susceptible to pertussis infection as adolescents or adults because of waning immunity.3 Adolescents and adults with untreated or unrecognized pertussis may transmit the infection to susceptible individuals, including neonates.4 Infected adults are contagious for 3 weeks from the onset of the cough or whoop or until 5 days after initiation of treatment with appropriate antibiotics.2 Neonates and infants up to 1 year of age who have not been vaccinated account for nearly 90% of deaths related to pertussis.5 Three doses of pertussis vaccine are needed to protect infants and children.6,7 Because of the significant morbidity and mortality associated with this infection, attempts to prevent pertussis are crucial. Postexposure prophylaxis against pertussis is effective in preventing symptomatic infection among asymptomatic contacts if the prophylaxis is given with- CASE SERIES No Infantile Hypertrophic Pyloric Stenosis among Neonates who Received Erythromycin for Postexposure Prophylaxis against Pertussis Brandi Newby, Maureen Cuddy, and Vibhuti Shah in 21 days after onset of cough in the index case.4 Macrolide antibiotics, including erythromycin, have been recommended for postexposure prophylaxis to decrease the risk of infection and its associated complications. 7 The choice of drug depends on the risks and benefits identified for the population to be treated. An additional consideration with erythromycin is the reported link between use of erythromycin and increased risk of infantile hypertrophic pyloric stenosis (IHPS).8-10 Erythromycin induces gastrointestinal motor activity, probably through binding to motilin receptors.11,12 The role of erythromycin in IHPS may be related to increased work of the smooth muscles leading to hypertrophy. 11 Some dose-dependent gastrointestinal effects of erythromycin have been noted, although a threshold dose associated with IHPS has not been identified.11,12 The cause of IHPS is unknown.11 An incidence of 2 per 1000 live births has been reported, but the incidence has also been reported to change over time in some geographic regions.13,14 Other factors associated with an increased risk include male sex, first-born child, white race, family history of the condition, and erythromycin use in neonates and infants less than 90 days of age.8-10,14,15 Preterm infants typically experience IHPS symptoms later than term infants; this observation is probably related to the development of functional motilin receptors, which are usually present after 32 weeks’ gestation.10,16,17 IHPS is usually diagnosed at about 1 month of age and rarely after 3 months of age, although it has been diagnosed during the neonatal period.13 The classical presentation of IHPS includes nonbilious projectile vomiting and irritability with feeding. In severe cases, dehydration, weight loss, and electrolyte abnormalities may occur.13 The objective of the case series reported here was to determine if the use of erythromycin for postexposure prophylaxis against pertussis in preterm and term neonates was associated with any cases of IHPS.