Acquired angioedema due to C1-inhibitor deficiency (C1–INH-AAE) is a rare disease
that can be diagnosed via complement testing. It often accompanies lymphoproliferative
underlying diseases. Our study aimed to examine if there is a connection between complement
parameters and the clinical symptoms of C1–INH-AAE, and, in case of a known underlying
disease, its activity. The other question is how a connection, if proven, could help
in the development of the therapeutic strategy of C1–INH-AAE patients. In the past
30 years, out of the 3938 patients sent to the Angioedema Center with angioedema symptoms,
we have diagnosed C1–INH-AAE in 19 cases. An underlying disease was diagnosed in 15
patients. Most often lymphoma (6/19 patients) and monoclonal gammopathy of undetermined
significance (6/19 patients) were found. Angioedema specific long-term prophylaxis
did not result in an improvement in neither the frequency of the attacks nor in the
complement parameters. A connection has been found between the presence and activity
of any underlying disease, the frequency of the angioedema attacks and the decreased
level of proteins of the complement system. Decreasing complement parameters warn
about the appearance or the worsening of the underlying disease. The treatment of
the underlying disease brings improvement in the complement parameters. Rituximab
treatment reduced the number of attacks or completely made them disappear, and we
experienced positive changes in complement parameters. Complement parameters supported
the long-term efficacy of rituximab treatment for C1–INH-AAE. The change in complement
parameters predict the relapse of the underlying disease, and it is a good indicator
for the prediction of angioedematous attacks. In C1–INH-AAE, it is essential to examine
the patients for underlying diseases, and to regularly follow up the patient's complement
parameters.
