Common variable immunodeficiency (CVID) is a heterogeneous group of primary immunodeficiency disorders characterized by defective antibody production, low levels of serum immunoglobulins and increased susceptibility to infection. The patient was a 39-year-old male who was admitted to the gastroenterology department with a two week history of diarrhea, blunt abdominal pain below the umbilicus, prolonged febrile state, loss of appetite and loss of body weight of 18 kg during the previous six months. Screening tests of serum immunoglobulins showed decreased concentrations of three types of immunoglobulins: IgA < 0.24 g/L, IgM < 0.18 g/L and IgG < 1.55 g/L. Lymphocytes immunophenotypisation revealed inversed CD4(+)/8(+) T cells ratio, 0.31 and absence of plasma cells (CD138 negative). Colonoscopy showed a rectal mucosa like cobblestones with multiple longitudinal and serpentinous ulceration, without involvement of other segments of the colon and the small intestine. Histopathology revealed aphtous ulcerative lesions, transmural inflammation with multiple lymphoid aggregates and benign lymphoid nodular hyperplasia of the small intestine. Plasma cells were absent from the lamina propria. Magnetic resonance imaging of a perianal fistula demonstrated a trans-sphicteric type. This case is specific because of the three illnesses associated and only one case of an association of diabetes mellitus type I and immunodeficiency reported thus far.