All IBD is Not Necessarily Sporadic IBD; A Case of Primary Immunodeficiency Mimicking Small Bowel Crohnʼs Disease

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The gastrointestinal (GI) tract is the largest immunological organ in the body. The GI tract contains majority of the lymphocytes and produces large amounts of immunoglobulin, protecting us from exposure to pathogens. There are over 150 heterogeneous primary immunodeficiencies and most of them are inherited. Immune defects can occur in the T cell line (cellular), B cell line (humoral), or both T and B cell lines. Dysfunction in immunity can lead to mucosal inflammation and GI distress. Thus, it is not uncommon for immunocompromised patients to present with GI symptoms. Immunocompetent and immunocompromised patients with gastrointestinal diseases can present with similar symptoms. However, immunocompromised patients have distinct histologic features and do not respond to conventional therapies. Therefore, it is critical for gastroenterologists to correctly diagnose and treat patients with immunodeficiency. Therapy for primary immunodeficiency: antibiotics, immunoglobulins, and rarely bone marrow transplantation. Herein, we report a 63-year-old male who was transferred from an outside hospital (OSH) for evaluation of Crohn Disease refractory to steroids and anti-TNF therapy. OSH work up revealed that this patient had recent exposure to Giardia. On admission, the patient was severely malnourished (albumin 0.9) with diffuse anasarca. He had multiple vitamin deficiencies due to malabsorption. MRE revealed active inflammatory small bowel disease. His hospital course was complicated by multiple infections, requiring intubation and broad spectrum antibiotics. Labs further revealed CD4 count 235, decreased absolute B cells, decreased immunoglobulins, decreased T regulatory cells, and absent NK function, suggestive of late onset combined immunodeficiency. His jejunal biopsies appeared similar to graft-versus-host disease. His biopsies were not consistent with Crohn Disease, lymphoma, or autoimmune enteropathy. He was started on monthly IVIG and sirolimus with partial recovery of his NK function. His infections resolved and he was discharged with TPN to rehab. Whole genomic sequencing was sent to determine a possible genetic link to his disease and is currently pending. This case demonstrates the importance of incorporating basic immunological work up in the assessment of patients with gut inflammation. It also suggests that individuals who present with an infection followed by gut inflammation may be more likely to have an immunodeficiency as opposed to sporadic IBD.