[TNFRSF13B gene mutation in adult patient with common variable immunodeficiency. Case report].

Common variable immunodeficiency (CVID) is one form of the primary immunodeficiencies (PIDs). CVID is characterized by variable clinical manifestations. Genetic alteration is a cause of the disease in many cases. In the current paper we described Patient N of 45 years old, who have been suffering from frequent various infections and therefore attended an immunologist and clinical geneticist. Immunoglobulins (Ig) A, M, and G deficiency was found in the patient. As a result of medical genetic counselling primary immunodeficiency has been suggested as a diagnosis. Further molecular genetic testing using clinical exome sequencing (Next Generation Sequencing method) revealed a likely-pathogenic variant c.204dupA (p.Leu69ThrfsX12, rs72553875) of TNFRSF13B gene in the patient. The gene variant was found in homozygous state. According to the international medical literature and genomic databases TNFRSF13B gene mutations lead to the CVID development and in some patients are characterized by isolated IgA deficiency and in the other group of patients can lead to decrease of IgA, IgM, and IgG. The patient had a family history of cancer and autoimmune inflammatory bowel disease (erosive-ulcerative enterocolitis). Moreover, one sibling of the patient died at the age of 3 weeks from complications of toxoplasmosis infection. The other sibling of 51 years old have been also suffering from recurrent infectious diseases. Thus, the genetic cause of the disease was identified in the proband. It has been shown that homozygosity for variant c.204dupA of TNFRSF13B gene is characterized by the deficiency of all three classes of Ig. Medical genetic counselling and modern molecular genetic methods application is an important step in management of people with signs of immunodeficiency. Such approach helps to make a diagnosis to the patient, to find an exact molecular reason of the condition, to use effective treatment, and to perform preventive measures in patient`s family.