[Staphylococcus aureus sepsis as an initial manifestation of common variable immunodeficiency].

Introduction: Common variable immunodeficiency (CVID) is the most common symptomatic immunodeficiency in adults, diagnosed by exclusion in cases of hypogammaglobulinemia without an identifiable cause. Its manifestations range from recurrent infections to autoimmunity and risk of malignancy.

Case report: A previously healthy 11-year-old female patient was originally from and resides at Rancho El Nogal in Arandas, Jalisco, a community of approximately 250 inhabitants. There was no significant family history; there was no known consanguinity or presence of genetic diseases in the family. Outcome: After trauma to the left leg, she developed osteomyelitis. Upon admission, pancytopenia, enlarged lymph nodes, hepatosplenomegaly, and abscesses with positive cultures for Staphylococcus aureus were detected. An approach to detecting inborn errors of immunity was initiated, revealing decreased immunoglobulin G and A levels. Due to the severe systemic infection, intravenous immunoglobulin was administered at 1 gram/kilogram, and the immunosuppression study was expanded. Abnormalities in the lymphocyte subpopulation were detected, with decreased CD19+ counts: 71 mm³, CD3+ counts: 915 mm³, CD4+ CD45RA+ T cells (naive): 92 mm³, total memory B cells (3%), non-isotype-switched (2.5%), isotype-switched (0.5%), plasmablasts (0.3%), and decreased CD21 counts (9%). The patient was classified as Freiburg 1B common variable immunodeficiency. Monthly intravenous immunoglobulin was started at a dose of 400 milligrams/kilogram. The patient responded favorably to immunoglobulin treatment, with no subsequent serious infections. She remains stable and is being monitored by immunologists.

Conclusion: CVID, although more common in adults, can present in children. S. aureus sepsis as an initial manifestation, as in this patients case, should raise concerns about possible underlying immunodeficiencies. This case highlights the importance of suspecting primary immunodeficiencies in patients with severe infections, underscoring the need for early diagnosis and treatment to optimize prognosis.