S5984 Congenital Diarrhea Associated With Diacylglycerol O-Acyltransferase 1 Deficiency: Unusual Presentation

Introduction: Diacylglycerol-O-acyltransferase-1 deficiency (DGAT1) is a rare congenital diarrheal disorder caused by abnormal lipid metabolism, evidenced by growth faltering, profuse diarrhea, vomiting, and metabolic disturbances in the first 3 months of life. Here, we report a male infant who presented with persistent emesis and was ultimately diagnosed with DGAT1 deficiency. Case Description/Methods: A term male infant presented at 4 weeks with persistent emesis and poor weight gain. Initial imaging was normal, but labs showed metabolic acidosis and hypoalbuminemia with normal fecal fat. Various alterations to feeds were ineffective. At 2 months, he developed watery diarrhea causing hypernatremic dehydration, secondary to a new rotavirus infection, but he recovered with no further diarrhea. Even so, he continued to have emesis and failure to thrive. Further investigation revealed reflux and delayed gastric emptying, and he was started on erythromycin. At 3.5 months, the patient’s emesis persisted and anthropometrics were concerning for severe malnutrition. More intensive lab workup was unrevealing. A repeat endoscopy was performed with pyloric botox; biopsies revealed duodenal congestion and lactase deficiency. Pancreatic stimulation test showed pancreatic insufficiency and pH impedance showed acid reflux. He had a gastric tube (G-tube) placed with amino-acid based formula feeding up to 165 kcal/kg/day, and was started on pancrelipase. Despite those efforts, he required total parenteral nutrition, which enabled him to gain weight. Stool studies were pertinent for low elastase, elevated fat, and stool pH 5, with normal alpha-1 antitrypsin (A1AT), reducing substances, and electrolytes. Genetic testing confirmed a DGAT1 mutation. He was then started on a low fat formula, with significant improvement. He has since been gaining weight with no emesis, now taking full feeds by mouth. Discussion: This case highlights the challenge of diagnosing DGAT1 deficiency congenital diarrhea. While our patient had symptoms of poor weight gain, vomiting, and hypoalbuminemia, he lacked the classic profuse diarrhea and endoscopic findings. However, it’s possible his diarrhea could have been mistaken for urine output. He had normal initial stool fat and normal stool A1AT, which diverted his workup away from malabsorption. Other diagnoses, including reflux, dysmotility, and exocrine pancreatic insufficiency delayed his diagnosis. Congenital diarrhea should be on the differential for infants with growth flattering even if diarrhea is not noted.