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).
