A193 DGAT1 DEFICIENCY WITHOUT DIARRHEA

Background

Acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1) catalyzes the final step in triglyceride (TG) synthesis and is highly expressed in enterocytes (EC). DGAT1 deficiency (DGAT1D) is a rare autosomal recessive protein losing enteropathy (PLE) classified as a congenital diarrheal disorder (CDD). Presumably, fat ingestion causes accumulation of DGAT1 substrates within the EC causing lipotoxicity-induced EC dysfunction and death.

Aims

Report a presentation of DGAT1D atypical for a CDD.

Methods

We present an infant with DGAT1D with protracted emesis and failure to thrive (FTT) in the absence of diarrhea despite enteral nutrition with varied fat containing formulas (FCF).

Results

A male infant presented with emesis and FTT requiring multiple admissions. He was initially diagnosed with cow’s milk protein allergy due to concurrent bloody stools, which resolved with hypoallergenic formula. Reportedly watery stools when exclusively breastfed became formed following switch to formula at 2 weeks of age. Interestingly, he subsequently required intermittent suppositories. However, emesis and malnutrition progressed, refractory to omeprazole, baclofen, and varied hypo- and non-allergenic FCF (all containing >0.02g/ml fat, mixtures of medium and long chain FA). He had persistently low serum albumin, ceruloplasmin, and IgG, but SA1AT was normal. TGs were normal, although not measured on FCF. Low fecal elastase (FE) normalized after nutritional support but sweat chloride was intermediate. CFTR sequencing revealed CFTR mutations S466X and R1070 in cis. TPN was started for severe malnutrition at 2 months. Emesis resolved while fasted or receiving enteral electrolyte solution.

Endoscopic biopsies on FCF showed increased lamina propria cellularity, no villous abnormalities in the duodenum, chronic inflammation in the gastric body, and normal colonic mucosa. Whole exome sequencing at 2 months showed homozygous c.838C>T (p.Arg280Ter) mutations in DGAT1, explaining his clinical presentation and biochemical features of PLE. After diagnosis, he was started on Tolerex® formula (fat = 0.017g/ml), which was tolerated.

Conclusions

DGAT1D is classified as a CDD, with vomiting often reported. This case describes a unique presentation of this rare condition, with emesis the predominant symptom, and notable constipation, demonstrating the variable phenotype of this condition. Fat malabsorption may contribute to constipation by altering viscosity of luminal contents or activating the ileal brake. Thus, DGAT1D should be considered on the differential for congenital PLE, even without diarrhea.

This case also demonstrates the limitations of stool testing in DGAT1D as random SA1AT concentrations may not reflect A1AT clearance in the diagnosis of PLE. Low FE has been detected in children with malnutrition or dietary restriction and has been reported in DGAT1D, where it likely represents a physiologic consequence of FTT.

Funding Agencies

None

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