Targeted Sequencing and Immunological Analysis Reveal the Involvement of Primary Immunodeficiency Genes in Pediatric IBD: a Japanese Multicenter Study.

PURPOSE: Pediatric inflammatory bowel disease (IBD) is a heterogeneous disorder caused by multiple factors. Although genetic and immunological analyses are required for a definitive diagnosis, no reports of a comprehensive genetic study of a Japanese population are available. METHODS: In total, 35 Japanese patients <16 years of age suffering from IBD, including 27 patients aged <6 years with very early-onset IBD, were enrolled in this multicenter study. Exome and targeted gene panel sequencing was performed for all patients. Mutations in genes responsible for primary immunodeficiency diseases (PID) and clinical and immunological parameters were evaluated according to disease type. RESULTS: We identified monogenic mutations in 5 of the 35 patients (14.3 %). We identified compound heterozygous and homozygous splice-site mutations in interleukin-10 receptor A (IL-10RA) in two patients, nonsense mutations in X-linked inhibitor of apoptosis protein (XIAP) in two patients, and a missense mutation in cytochrome b beta chain in one patient. Using assays for protein expression levels, IL-10 signaling, and cytokine production, we confirmed that the mutations resulted in loss of function. For each patient, genotype was significantly associated with clinical findings. We successfully treated a patient with a XIAP mutation by allogeneic cord blood hematopoietic stem cell transplantation, and his symptoms were ameliorated completely. CONCLUSIONS: Targeted sequencing and immunological analysis are useful for screening monogenic disorders and selecting curative therapies in pediatric patients with IBD. The genes responsible for PID are frequently involved in pediatric IBD and play critical roles in normal immune homeostasis in the gastrointestinal tract.

Phenotypic characteristics of pediatric inflammatory bowel disease in Japan: results from a multicenter registry.

BACKGROUND/AIMS: There are few published registry studies from Asia on pediatric inflammatory bowel disease (IBD). Registry network data enable comparisons among ethnic groups. This study examined the characteristics of IBD in Japanese children and compared them with those in European children. METHODS: This was a cross-sectional multicenter registry study of newly diagnosed Japanese pediatric IBD patients. The Paris classification was used to categorize IBD features, and results were compared with published EUROKIDS data. RESULTS: A total of 265 pediatric IBD patients were initially registered, with 22 later excluded for having incomplete demographic data. For the analysis, 91 Crohn's disease (CD), 146 ulcerative colitis (UC), and 6 IBD-unclassified cases were eligible. For age at diagnosis, 20.9% of CD, 21.9% of UC, and 83.3% of IBD-unclassified cases were diagnosed before age 10 years. For CD location, 18.7%, 13.2%, 64.8%, 47.3%, and 20.9% were classified as involving L1 (ileocecum), L2 (colon), L3 (ileocolon), L4a (esophagus/stomach/duodenum), and L4b (jejunum/proximal ileum), respectively. For UC extent, 76% were classified as E4 (pancolitis). For CD behavior, B1 (non-stricturing/non-penetrating), B2 (stricturing), B3 (penetrating), and B2B3 were seen in 83.5%, 11.0%, 3.3%, and 2.2%, respectively. A comparison between Japanese and European children showed less L2 involvement (13.2% vs. 27.3%, P< 0.01) but more L4a (47.3% vs. 29.6%, P< 0.01) and L3 (64.8% vs. 52.7%, P< 0.05) involvement in Japanese CD children. Pediatric perianal CD was more prevalent in Japanese children (34.1% vs. 9.7%, P< 0.01). CONCLUSIONS: Upper gastrointestinal and perianal CD lesions are more common in Japanese children than in European children.