Introduction: X-linked agammaglobulinemia (XLA) is an inborn error of immunity, caused by mutations in the BTK gene; It is characterized by alteration in the production of antibodies due to the interruption in the development of B cells, predisposing to invasive infections by encapsulated bacteria. Here we present an XLA case confirmed by laboratory studies and by sequencing.
Case presentation: 8-year-old male patient, with a history of hospitalization for severe pneumonia at 9 months of age. During the first three years of life he had otitis media and repeated pharyngeal and diarrheal symptoms. Maternal uncle who died at an early age of unknown cause, a 6 years brother with X-linked agammaglobulinemia confirmed. In the diagnostic approach, leukopenia, lymphopenia, hypogammaglobulinemia (IgA, IgE, IgM, IgG) and decreased lymphocyte subpopulations (CD19 of 0.19%) were identified. The presence of a missense variant in BTK was identified by exome sequencing. Immunoglobulin replacement therapy was started, which is maintained to date. Since the start of replacement therapy, he has presented one episode of non-serious pneumonia and two gastrointestinal episodes without dehydration that required hospitalization and broad-spectrum antibiotic coverage. He currently remains stable, without infection in the last year, no need for antibiotic prophylaxis and IgG values within the normal range for his age.
Discussion: XLA should be suspected in all male patients from 6 months of age with recurrent infections by encapsulated bacteria, with hypotrophic lymphoid tissue, with agammaglobulinemia, and with a history of deaths of siblings, uncles, or maternal cousins. Early diagnosis is essential for the timely initiation of immunoglobulin replacement therapy and strict follow-up, which makes it possible to guarantee a normal quality of life, and prevent infections that lead to complications that increase morbidity and mortality. The identification of the altered gene is also important to provide genetic counseling to the family.