Granulomatous Lung Diseases (GLD) comprises a wide range of infectious and non-infectious pathologies that present the same pattern of chronic inflammatory response [1].
The granulomas emerge after an attempt of the cellular immune response to contain an agent of difficult eradication.
Histologically,
granulomas consist of an aggregation of macrophages that transform into epithelioid cells,
surrounded by monocytes – mainly lymphocytes [2].
Mycobacterial and fungal infections are the most common infectious causes of GLD,
including tuberculosis (TB),
nontuberculous mycobacteriosis,
Histoplasma,
Cryptococcus,
Coccidioides,
Blastomyces and Aspergillus [2].
Non-infectious GLD might be the result of several different physiopathological conditions [3],
including inflammatory diseases,
such as sarcoidosis; exposure related lung diseases,
such as hypersensitivity pneumonitis; vasculitis,
most commonly granulomatosis with polyangiitis; autoimmune disorders,
such as rheumatoid nodules; and also associated with malignancies [2,
4].
Granulomatous inflammation has been occasionally found associated with some neoplastic diseases,
including lung cancer,
and is usually attributed to a ‘sarcoid reaction’,
although some authors also suggest a possible correlation with a previous granulomatous lung infection,
specially in endemic areas [5,
6].
Finally,
there are granulomatous lesions of uncertain etiology,
comprising a group known as Granulomatous Lesions of Unknown Significance - GLUS.
This term was used for the first time in 1990 to designate biopsies whose results contained epithelioid granulomas without a definitive cause,
even after subsequent investigation [7].
The incidence of GLD vary according to geographical location and ethnical features of the population,
which might influence not only the occurrence of infectious GLD but also non-infectious causes,
including exposure related GLD and autoimmune diseases.
Imaging findings of GLD might be much similar despite the cause,
but particularities of each etiology influence the radiological features and corroborate when a confident pathological diagnosis is not possible.
This study aimed to outline the incidence of the etiologies of biopsy proven GLD in a tertiary hospital in Sao Paulo,
Brazil,
as well as its correlation with the imaging findings.