In rare cases, angioedema becomes
manifest as a result of acquired C1-INH deficiency.
Recurrent
angioedema due to an acquired C1-INH deficiency (AAE) may be
associated with a lymphoproliferative disorder or other malignant
disease (AAE type I). Usually, these are malignant disorders of
the B-lymphocyte system with monoclonal gammopathy and anti-idiotypic
antibodies. The immune complexes consisting of monoclonal and
anti-idiotypic antibodies result in an increased activation of C1
and consequently in an increased consumption of C1-INH which then
is no longer available in adequate amounts for its other
functions. Like HAE, AAE is also characterized by low
concentrations or absence of C2, C4 or functionally active C1-INH.
In contrast to the hereditary form, in acquired angioedema there
is a marked drop in C1 concentration and symptoms usually start
in middle aged patients.
A further
type of acquired C1-INH deficiency is caused by antibodies to C1-INH
(IgG or IgM) (AAE type II).
In
acquired angioedema due to C1-INH deficiency, the same laboratory
tests should be carried out as in HAE, in particular C1. In
addition, the patients should be thoroughly examined to exclude
malignant lymphomas, paraproteinemias and other B-cell disorders
(AAE type I), as well as to identify auto-antibodies to C1-INH (AAE
type II).
In the
first form of acquired angioedema (AAE type I), treatment of the
underlying disorder is the primary consideration. Epsilon-aminocaproic
acid or tranexamic acid are effective in some patients with AAE
due to C1 inhibitor deficiency.
Emergency
treatment of the obstruction of the upper airways corresponds to
that employed in hereditary angioedema.
