Antibody Deficiency in Xeroderma Pigmentosum.

We describe a 3-year-old patient with xeroderma pigmentosum (XP) and genetically confirmed XPA deficiency who presented with recurrent infections in early childhood. Immunological assessment revealed mild hypogammaglobulinemia with IgG2 and IgG3 subclass deficiencies, as well as impaired humoral immunity demonstrated by a reduced antibody response to repeated vaccinations against bacterial antigens. Flow cytometric analysis further showed an altered distribution of peripheral T helper (TH) cell subsets. In addition, we report a second case: a 33-year-old XP patient with ERCC4 deficiency who also exhibited IgG3 subclass deficiency and reduced response to booster vaccination. Functional studies revealed defective nucleotide excision repair (NER) following UV-C exposure, along with reduced B-cell activation capacity. These findings suggest a potential link between XP and immunoglobulin subclass deficiencies, indicating a susceptibility to infections in affected individuals. We therefore recommend that patients diagnosed with XP undergo comprehensive immunological evaluation to allow early detection of immunodeficiency and timely intervention, including booster vaccinations or prophylactic measures such as low-dose antibiotics or immunoglobulin replacement therapy when indicated.