Interstitial Pneumonia Associated with the Influenza Vaccine: A Report of Two Cases

Hibino, Makoto; Kondo, Tetsuri

In the two cases described above, the patients were never smokers and had no history of allergy, recent visits abroad, or inhalation exposure. In addition, they reported no family history of pulmonary, allergic, or connective tissue diseases. Their serological tests were negative for several autoimmune markers such as antinuclear antibody, anti-double stranded DNA, anti-SS-A antibody, anti-SS-B antibody, anti-Scl-70 antibody, anti-centromere antibody, anti U1ribonucleoprotein (RNP) antibody, anti-aminoacyl tRNA synthetase antibodies (including anti-Jo1 antibody), rheumatoid factor, anti-cyclic citrullinated peptide antibody, and anti-neutrophil cytoplasmic antibodies (proteinase-3 and myeloperoxidase In contrast, they met all of the following diagnostic criteria for drug-induced interstitial lung disease: correct identification of the drug; singularity of the drug; temporal eligibility; characteristic clinical, imaging, BALF, and pathological patterns of the reaction to the specific drug; and exclusion of other causes (5) . Based on these findings, interstitial pneumonia associated with the influenza vaccine was diagnosed after excluding other causes of secondary interstitial pneumonia, such as infectious and connective tissue disease. The pathophysiology of drug-induced interstitial pneumonia, although not obvious, is believed to be cytotoxic or immune-mediated lung injury. The present two cases of interstitial pneumonia showed immune-mediated lung injury, as indicated by the lymphocytic and eosinophilic BALF and pathological findings of organizing pneumonia with alveolitis, positive DLST results for the influenza vaccine, and a good response to glucocorticoid therapy.