Table 4
Causes of secondary immune deficiencies in children, with associated immune system defect (defect in innate or physiological barriers, predominantly T-cell defect, predominantly antibody defect) and presenting features
| Cause | Defect | Presentation | ||
|---|---|---|---|---|
| Defect in Innate immunity or physiological barriers |  | Breach of anatomical and physiological barriers7 | For example, central lines, burns, eczema, mechanical ventilation | Increased risk bacterial infections especially staphylococcus and pseudomonas |
| Splenectomy/congenital asplenia or polysplenia | Defect in splenic function including role of phagocytes in clearing encapsulated bacteria8 | Post surgery or part of congenital abnormality – increased risk infections with encapsulated bacteria, particularly strep pneumonia | ||
| Predominantly T cell defect |  | HIV | CD4 T-cell depletion | Multiple but commonly pneumococcal bacteraemia (at all levels of CD4 counts) as well as respiratory and skin manifestations and opportunistic organisms (with significant immune depression) for example, tuberculosis, pneumocystis carinii pneumonia, cytomegalovirus |
| Malnutrition | Complex probably T cell mediated immunity8 | Particularly increased risk pneumonia, measles and tuberculosis | ||
| Leukaemia/Lymphoma | Marrow and lymphoid infiltration affecting number and function of immune cells | Multiple presentations depending on underlying cause – can present with infection particularly bacterial infections as functionally neutropenic as well as opportunistic infections | ||
| Immunosuppressive and Immune mediating drugs | Corticosteroids—wide ranging effects by inducing or suppressing gene transcription Biologics e.g. anti- TNFα agents (Infliximab, etanercept) Cytotoxic—inhibit DNA synthesis and suppress dividing cells for example, tumour, lymphocytes Cyclosporine, tacrolimus interfere with T cell signalling, inhibiting T cell proliferation | Increased risk multiple organisms including viral and fungal Intracellular bacteria particularly TB and salmonella Toxic effects on other organs Multiple risk for infection Impaired function against intracellular bacteria, for example, mycobacterium and salmonellae and opportunistic infection | ||
| Predominantly antibody defect |  | Prematurity | Reduced maternal IgG transfer during the third trimester, reduced neutrophil bone marrow pool and complement function | Increased risk intracellular bacteria (Salmonella, Listeria monocytogenes) and polysaccharide encapsulated organisms |
| Nephrotic syndrome | Multiple—decreased perfusion of the spleen, urinary loss of complement factor and immunoglobulin, immunosuppressive drugs8 | Increased risk encapsulated bacteria particularly pneumococcal spontaneous bacterial peritonitis |