Abstract
Protein-Losing Enteropathy (PLE) is the loss of protein through the gastrointestinal tract, subsequently leading to low levels of protein in the serum. The differential diagnosis for PLE is broad, and treatment is based on identifying and appropriately treating the underlying cause of the PLE. A 2-year-old boy presented with diarrhea, vomiting, edema, anemia, hypoalbuminemia, low serum IgG, and elevated stool alpha-1-antitrypsin, concerning for PLE. Endoscopy/colonoscopy showed mild reactive changes in the gastric and duodenal mucosa and was otherwise normal with no evidence of autoimmune enteropathy. MRI abdomen was negative for mesenteric lymphatic malformations. Echocardiogram showed a structurally normal heart. Urine CMV PCR was positive, and he was treated with valganciclovir for suspected Menetrier's disease, with no improvement in symptoms. He was incidentally noted to be hypoglycemic and subsequently admitted with profoundly labile blood glucose requiring glucagon and continuous glucose infusions. Further workup demonstrated hyperinsulinism, up-trending liver enzymes with normal international normalized ratio, and coagulopathy with low factor 11 and antithrombin with PICC-associated DVT. The constellation of PLE, transaminitis, hyperinsulinemic hypoglycemia, and coagulopathy was concerning for a congenital disorder of glycosylation (CDG). Transferrin glycosylation studies showed a CDG type I pattern and were confirmed via genetic testing with biallelic variants in the mannose phosphate isomerase (MPI) gene, which established the diagnosis of mannose phosphate isomerase-congenital disorder of glycosylation (MPI-CDG). Mannose therapy resulted in complete resolution of his edema, diarrhea, hypoalbuminemia, transaminitis, and hypoglycemia. CDGs include over 100 monogenic diseases with defects in the synthesis of oligosaccharides. Though a rare cause of PLE, MPI-CDG is an important consideration in the differential given the availability of an effective therapy. Treatment is well-tolerated and highly effective. In the case presented, the patient began showing symptomatic and biochemical improvement within a week of initiating therapy.