title: Inflammatory bowel disease and T cell lymphopenia in G6PC3 deficiency.
abstract: OBJECTIVE
  G6PC3 deficiency presents as a complex and heterogeneous syndrome that classically associates severe congenital neutropenia with cardiac and urogenital developmental defects. Here we investigate the findings of T cell lymphopenia and inflammatory bowel disease in a child with G6PC3 deficiency due to compound heterozygous mutations in intron 3 (c.IVS3-1 G>A) and exon 6 (c.G778G/C; p.Gly260/Arg).
  
  
  METHODS
  Histological examination was conducted on all biopsy specimens. Immunophenotyping and lymphocyte proliferation assays were performed. Immunoglobulin levels and vaccine responses were measured.
  
  
  RESULTS
  The patient showed persistent global T cell lymphopenia, with only 8 to 13 % of thymic naive CD31(+)CD45RA(+) cells among CD4 T cells (normal range 27-60 %). Proliferation assays and vaccine responses were within normal limits. The gastrointestinal inflammatory lesions were very closely related to those of glycogen storage disease type 1b, with a Crohn's-like appearance but without granuloma or increased cryptic abscesses. The gastrointestinal disease responded to infliximab therapy. These findings were associated with a polyclonal hypergammaglobuliemia G.
  
  
  CONCLUSIONS
  G6PC3 deficiency may present with inflammatory bowel disease and T cell lymphopenia. The diagnosis should thus be considered in a patient with chronic congenital neutropenia and gastrointestinal symptoms. Patients with confirmed disease should also undergo T cell phenotyping to rule out cellular immunodeficiency.
authors.affiliation: Department of Pediatrics, CHU Sainte-Justine and Université de Montréal, Montreal, Canada.
authors.forename: Philippe
authors.initials: P
authors.lastname: Bégin
authors.forename: Natalie
authors.initials: N
authors.lastname: Patey
authors.forename: Pascal
authors.initials: P
authors.lastname: Mueller
authors.forename: Andrée
authors.initials: A
authors.lastname: Rasquin
authors.forename: Alain
authors.initials: A
authors.lastname: Sirard
authors.forename: Christoph
authors.initials: C
authors.lastname: Klein
authors.forename: Elie
authors.initials: E
authors.lastname: Haddad
authors.forename: Éric
authors.initials: É
authors.lastname: Drouin
authors.forename: Françoise
authors.initials: F
authors.lastname: Le Deist
mesh_terms: D000293:Adolescent; D002648:Child; D005753:Gastric Mucosa / Q000473:pathology; D005952:Glucose-6-Phosphatase / Q000235:genetics* / Q000276:immunology; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000150:complications* / Q000235:genetics* / Q000276:immunology; D007413:Intestinal Mucosa / Q000473:pathology; D018655:Lymphocyte Count; D008231:Lymphopenia / Q000150:complications* / Q000235:genetics* / Q000276:immunology; D009154:Mutation
chemical_list: D005952:Glucose-6-Phosphatase; C492193:G6PC3 protein, human