[Familial summer-type hypersensitivity pneumonitis in a grandfather and his two-and-a-half-year-old grandson].

We encountered a family in which two of the six members, the grandfather and his grandson, had summer-type hypersensitivity pneumonitis in late summer. Chest computed tomography of these patients showed small, diffuse nodular shadows in both lung fields, with mosaic-like opacities in the grandfather and ground glass opacity of both lung fields in the grandson. Bronchoalveolar lavage fluid from the grandfather disclosed high total cell counts, high percentages of lymphocytes, and a low ratio of CD 4+ cells to CD 8+ cells. Transbronchial lung biopsy specimens obtained from the same patient revealed alveolitis with non-caseous epithelioid cell granulomas in the interstitium and Masson bodies in the alveolar septa. These two patients recovered spontaneously after hospital admission. They had positive results in provocation tests for their home and were positive for serum anti-Trichosporon cutaneum (T. asahii, T. mucoides) antibodies. Both cases were accordingly diagnosed as summer-type hypersensitivity pneumonitis.