Introduction:

the common variable immunodeficiency is classified in group III of IX, which includes immunodeficiencies with a predominance of antibody deficiency. It is known that the mutation in the TNFSF13B gene, responsible for encoding the TACI protein, causes a variable clinical expression that accompanies the disease.

Case report:

a 25-year-old female patient, who started her condition from birth, was studied for chronic diarrhea without a definite etiology; the symptomatology was worsened by presenting decreased stools in consistency. The common variable immunodeficiency was made, and replacement therapy with intravenous immunoglobulin G was initiated every four weeks with significant clinical improvement. Next-generation DNA sequencing (NGS) of complete DNA exome was realized with a variant identification in TNFRSF13B, in exon 3 c.310T> C; p.cys104Arg.

Conclusions:

the clinical presentation of the shared variable immunodeficiency is diverse; within the clinical study of a patient suspected of this disease, it is essential to consider the presence and evolution of gastrointestinal symptoms. The molecular diagnosis of innate immunity errors helps clarify the pathophysiology of this group of diseases.