Familial Summer-type Hypersensitivity Pneumonitis: A Review of 25 Families and 50 Cases in Japan.

Summer-type hypersensitivity pneumonitis (SHP) is the most common form of pneumonitis in Japan; it accounts for 74% of all cases. It has been reported that 19.5-23.8% of SHP cases occur in families who live in the same house. We present our SHP cases and review 50 familial cases in 23 families that were reported in Japan (including our own) and 48 cases that were previously described in 22 articles published between January 1982 and October 2011. To the best of the authors' knowledge, this is the first review article in English to document the familial occurrence of SHP in Japan.