Common variable immunodeficiency (CVID) and other antibody deficiencies like immunoglobin G
subclass deficiency and selective IgM deficiency are the most frequent clinically significant
primary immunodeficiencies (PID) in adults. Prevalence in France in 2009 was 2.11/100.000
people.
These immunodeficiencies are characterized by a significant decrease in serum immunoglobulin
concentrations and antibodies production. In some patients, qualitative and/or quantitative
alterations in B cells repertoire and sometimes in T cells repertoire are observed.
Consequently, patients are more prone to bacterial infections, respiratory manifestations,
auto-immune diseases, atopic manifestations, neoplastic complications. Respiratory
manifestations are the main complication responsible for the morbidity and mortality in PHID.
Bronchiectasis are one of the observed pulmonary complications. It is characterized by
pathological and permanent dilatation of the airways, as demonstrated by a thoracic CT-scan.
Its frequency varies from a study to another, ranging from 20% to 60% in different PHID
populations. Some patients with bronchiectasis can be asymptomatic, while others can present
daily symptoms of cough and sputum production with periodic worsening of their symptoms
(exacerbations). It can lead to chronic respiratory failure, more infectious complications
and altered quality of life. Moreover, mortality in patients with bronchiectasis (whatever
the cause) is twice as high than in general population.
A thoracic CT-scan is therefore recommended at PHID diagnosis. However, there is no
recommendation concerning screening of this complication during follow-up.
Pathophysiology of bronchiectasis in general is described as a cycle of events promoting
impaired mucociliary clearance and retention of airways secretions, leading to chronic
infection and thus to inflammatory response, leading to abnormal remodeling oh the airways.
To date, it is not known if some PHID patients are more prone to developing bronchiectasis.
There is no statistical link with the number of past infectious events. Some studies
suggested that patients with lower IgM concentration or lower switched memory B cell might be
more at risk.
Concerning T-cell subset, polarization of CD4 T helper cells response as well as T follicular
helper implication might be of interest. Indeed, in auto-immune manifestations in patients
with primary immunodeficiency, T follicular helper cells (T cells implied in regulation of B
-cells response in germinal centers) are sometimes impaired.
Another interesting phenomenon has been described in chronic obstructive pulmonary disease
(another pulmonary disease, presenting similar clinical and pathophysiological mechanisms
with bronchiectasis), where lung-infiltrating inflammatory cells secrete proteases
participating in elastin breakdown a specific marker of elastin degradation genesis of
elastin-derived peptides. These peptides modulate CD4+ T cell (T helper) response and
pro-inflammatory cytokine production. As inflammatory response in patients with PHID can
differ from immunocompetent patients, modulation of pro-inflammatory T helper cell response
by elastin-derived peptides might also be different, participating in the abnormal remodeling
of the airways.
In the Champagne-Ardenne region, PHID prevalence is high (5.37/100.000 habitants), however,
we do not have data concerning bronchiectasis prevalence in this population and its
repercussion on respiratory function and quality of life for our patients. Moreover, a better
understanding of pathophysiology and factors associated with the presence of bronchiectasis
may lead to better and more personalized care (diagnostic and therapeutic).