Immunodeficiency in the differential diagnosis of interstitial lung diseases

Interstitial lung processes (IPP), or diffuse parenchymal lung diseases, are a broad group of diseases characterized by varying degrees of pulmonary fibrosis and inflammation affecting predominantly, but not exclusively, pulmonary interstitium. IPP mostly occur in adulthood with maximum manifestation between 40 and 70 years of age. Although IPP mostly present as a primary diagnosis, they also belong to the portfolio of pulmonary disorders in patients with primary immunodeficiencies. The authors present case reports of patients with interstitial lung involvement and primary immunodeficiencies [particularly those manifesting also in adulthood, such as common variable immunodeficiency (CVID), and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) deficiency]. In addition, we report the case of silico-sis patient with severe lymphopenia. Therefore, in patients with newly diagnosed interstitial lung disease, congenital immune system disorder should be considered. Basic immunological laboratory examination of humoral and cellular immunity should be an essential part of the differential diagnosis algorithm for interstitial lung disease.