WD Repeat Domain 1 (WDR1) Deficiency Presenting as a Cause of Infantile Inflammatory Bowel Disease

ABSTRACT Infantile and very early onset inflammatory bowel disease (VEOIBD) are a rare phenomenon wherein patients develop intestinal inflammation with typical IBD symptoms before ages 2 and 6, respectively. In recent years, there has been an increasing number of monogenetic immunological disorders identified that lead a child to develop VEOIBD. We present a case of an infant boy who presented with hematochezia and thrombocytopenia in the first week of life and developed IBD by the age of 1 month. Additional clues to his diagnosis included lymphopenia and nuclear herniation observed in his neutrophils. Compound heterozygous damaging variants were identified in WD Repeat Domain 1 (WDR1) by whole‐exome sequencing (WES) and represents a novel cause of VEOIBD. Our patient's IBD and immunologic phenotype was successfully treated by hematopoietic stem cell transplant (HSCT).