Background: Infantile hypertrophic pyloric stenosis refractory to initial complete pyloromyotomy is extremely rare and distinguished from incomplete pyloromyotomy by a prolonged postoperative symptomatic improvement before symptom recurrence. The pathogenesis is uncertain but is theorized to be a continuation of the process that initially produces infantile hypertrophic pyloric stenosis (IHPS), which has been associated with chromosome region 9q duplications. Case Presentation: Here we present a case of a neonate presenting with respiratory distress syndrome, hydronephrosis, pulmonary valve stenosis, and hypotonia at birth. A microarray identified a deletion of the terminal region of chromosome 9q, consistent with Kleefstra syndrome. The infant was diagnosed with pyloric stenosis after abdominal ultrasound was ordered to investigate difficulties with feeding, vomiting, and poor weight gain. Following initial surgical repair at five weeks of age, the infant demonstrated consistent postoperative weight gain for six weeks and resolution of emesis. However, vomiting returned and weight gain halted during weeks eleven and twelve of life; a barium swallow series and repeat abdominal ultrasound demonstrated recurrent IHPS. The infant underwent repeat pyloromyotomy and with post-operative clinical improvement. Conclusions: We present the first known case of recurrent pyloric stenosis in a patient with Kleefstra syndrome, and which further supports the hypothesis of an association between chromosome 9 and pyloric stenosis, due to an increased incidence of pyloric stenosis in chromosome 9 pathologies such as Kleefstra Syndrome found in current literature.

This a preprint and has not been peer reviewed. Data may be preliminary.