Common variable immunodeficiency (CVID) is a primary immunodeficiency disorder characterized by decreased levels of circulating immunoglobulins (Ig) and increased susceptibility to infections. We describe the case of a girl, progressively developing CVID, whose first clinical manifestations were noninfectious diffuse pulmonary infiltrates and rapidly developing hilar and mediastinal lymphadenopathies causing a severe "superior vena caval syndrome". Histological evaluation of surgical samples showed follicular and paracortical hyperplasia of the lymph nodes and poorly organized, non-necrotizing, noninfectious, "reactive" granulomata in lymph nodes and pulmonary tissue. Daily treatment with azathioprine and prednisone induced resolution of the intrathoracic abnormalities but was associated with a progressive decrease of circulating IgG and IgA levels and natural killer (NK) lymphocytes that was not related to treatment. This case demonstrates that granulomatous inflammatory changes may be the first manifestations of common variable immunodeficiency, and that this disorder must be included in the differential diagnosis of lymphoid interstitial pneumonitis and of bilateral mediastinal lymph node enlargement leading to superior vena caval syndrome.