The three main forms are congenital, idiopathic, and cyclic neutropenia. Congenital
forms are typically apparent at birth or during early childhood and are considered the
most severe form. Chronic idiopathic neutropenia usually affects adults. However,
in some cases, the disorder has been demonstrated during childhood, but remains clinically
undetected until adulthood. Cyclic neutropenia in most cases is thought to be
present at birth. However, in some cases, symptoms may not become apparent until
childhood, adolescence, or even early adulthood. The disorder may also be acquired.