The consequences of deficiencies of the immune system
include recurrent infections, autoimmunity and susceptibility
to malignancy. Immune deficiency may arise
through intrinsic defects in immune function, but is
much more commonly due to secondary causes, including
infection, drug therapy, malignancy and ageing.
This chapter gives an overview of the rare primary
immune deficiencies. More than a hundred genetically
determined deficiencies have been described, most of
which present in childhood or adolescence. The clinical
manifestations are dictated by the component of
the immune system involved (Box ), but there is
considerable overlap and redundancy in the immune

box-4-4

network so some diseases do not fall easily into this
classification.