Abstract: A 77-year-old male presented with recurrent red rash, erosion, previously misdiagnosed as eczema, dermatitis, or cutaneous neoplasia. Upon admission, lymphocyte subset analysis revealed a deficiency in B lymphocytes and severe hypogammaglobulinemia (IgG 2.49 g/L). Histopathological examination of the skin lesions, combined with MetaCAP^TM high-throughput nucleic acid sequencing for pathogenic microorganisms, confirmed a diagnosis of HSV-2 infection with concurrent bacterial co-infection. The final diagnoses included herpes simplex virus 2 infection, B lymphocyte deficiency, and bacterial infection (primarily Staphylococcus aureus and Staphylococcus lugdunensis). Following comprehensive treatment with antiviral agents, antibacterial therapy, and immunomodulatory support, the patient's clinical symptoms improved significantly.

Key words: herpes simplex virus 2, B-cell deficiency, high-throughput sequencing, immune dysfunction