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

Defect in Innate immunity or physiological barriersEmbedded ImageBreach of anatomical and physiological barriers7For example, central lines, burns, eczema, mechanical ventilationIncreased risk bacterial infections especially staphylococcus and pseudomonas
Splenectomy/congenital asplenia or polyspleniaDefect in splenic function including role of phagocytes in clearing encapsulated bacteria8Post surgery or part of congenital abnormality – increased risk infections with encapsulated bacteria, particularly strep pneumonia
Predominantly T cell defectEmbedded ImageHIVCD4 T-cell depletionMultiple 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
MalnutritionComplex probably T cell mediated immunity8Particularly increased risk pneumonia, measles and tuberculosis
Leukaemia/LymphomaMarrow and lymphoid infiltration affecting number and function of immune cellsMultiple presentations depending on underlying cause – can present with infection particularly bacterial infections as functionally neutropenic as well as opportunistic infections
Immunosuppressive and Immune mediating drugsCorticosteroids—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 defectEmbedded ImagePrematurityReduced maternal IgG transfer during the third trimester, reduced neutrophil bone marrow pool and complement functionIncreased risk intracellular bacteria (Salmonella, Listeria monocytogenes) and polysaccharide encapsulated organisms
Nephrotic syndromeMultiple—decreased perfusion of the spleen, urinary loss of complement factor and immunoglobulin, immunosuppressive drugs8Increased risk encapsulated bacteria particularly pneumococcal spontaneous bacterial peritonitis