According to a European registry study, the mean age at onset of symptoms was 26.3 years old. As per the criteria laid out by ESID (European Society for Immunodeficiencies) and PAGID (Pan-American Group for Immunodeficiency),<unk>  is diagnosed if: * the person presents with a marked decrease of serum IgG levels (+, a T-cell marker, and decreased circulation of regulatory T cells and iNKT cell. Notably, approximately 10% of people display CD4+ T cell counts lower than 200 cells/mm3; this particular phenotype of<unk>  has been named LOCID (Late Onset Combined Immunodeficiency), and has a poorer prognosis than classical<unk> . Types Type OMIM Gene<unk> 1 ICOS<unk> 2 TACI<unk> 3 CD19<unk> 4 TNFRSF13C<unk> 5 CD20<unk> 6 CD81 The following types of<unk>  have been identified, and correspond to mutations in different gene segments.
Common variable immunodeficiency
Severe combined immunodeficiency
X-linked severe combined immunodeficiency
X-linked agammaglobulinemia
Chronic granulomatous disease
Primary immunodeficiency
Wiskott–Aldrich syndrome
Combined immunodeficiencies