Cause of this<unk>  is divided into primary and secondary: * Primary the International Union of<unk> logical Societies classifies primary<unk> <unk> es of the<unk>  system as follows: Hyper-IgM syndromes<unk> globulin M) :* Absent B cells with a resultant severe reduction of all types of antibody: X-linked agammaglobulinemia (btk<unk> , or Bruton's agammaglobulinemia), μ-Heavy chain<unk> , l 5<unk> , Igα<unk> , BLNK<unk> , thymoma with<unk><unk>  :* B cells low but present, but with reduction in 2 or more isotypes (usually IgG & IgA, sometimes IgM): common variable<unk><unk>  (CVID), ICOS<unk> , CD19<unk> , TACI (TNFRSF13B)<unk> , BAFF receptor<unk> . :* Normal numbers of B cells with decreased IgG and IgA and increased IgM: Hyper-IgM syndromes :* Normal numbers of B cells with isotype or light chain<unk> es: heavy chain deletions, kappa chain<unk> , isolated IgG subclass<unk> , IgA with IgG subsclass<unk> , selective<unk> globulin A<unk>  :* Transient hypogammaglobulinemia of infancy (THI) * Secondary secondary (or acquired) forms of<unk>  are mainly due to hematopoietic malignancies and infections that disrupt the<unk>  system: :*Multiple myeloma :*Chronic lymphoid leukemia :*AIDS
Humoral immune deficiency
T cell deficiency
IgG deficiency
Inborn errors of immunity
Neutrophil-specific granule deficiency
Inherited disorders of trafficking
Surfactant metabolism dysfunction
Mendelian susceptibility to mycobacterial disease