| Liebow [1] | Tubbs [3] | Yousem [5] | Ryu [6] | Total | |
| Cases n | 18 | 26 | 36 | 23 | 103 |
| Males/females n | 10/8 | 17/9 | 26/10 | 11/12 | 64/39 |
| Age at onset years median (interquartile range) | 45 (16–63) | 51 (24–75) | 42 (17–67) | 46 (26–69) | 46 (16–75) |
| Smoking history | ns | 15/26 (58) | 30/33 (91) | 20/23 (87) | 65/82 (79) |
| Mean smoking exposure pack-years (95% CI) | ≥10 | 36 (10–71) | 31 (10–90) | ||
| Occupational history, cases exposed | 1 exposed to plastic fumes and dusts 2 exposed to hairsprays | ns | ns | No environmental exposure or underlying disease identified | |
| Symptoms | |||||
| Dyspnoea | 18/18 (100) | 23/26 (88.5) | 29/34 (85) | 20/23 (87) | 90/101 (89) |
| Cough | 14/16 (87.5) | 18/26 (75) | 26/32 (81) | 10/23 (43) | 68/97 (70) |
| Sputum | 4/16 (25) | ns | 17/33 (52) | ns | 21/49 (43) |
| Weight loss | 6/10 (60) | 1/26 (4) | ns | ns | 7/36 (20) |
| Chest pain | 9/12 (75) | 1/26 (4) | ns | 4/23 (17) | 14/61 (23) |
| Haemoptysis | 1/18 (5.5) | 2/26 (8) | ns | ns | 3/44 (7) |
| Asymptomatic | 0/18 (0) | 1/26 (4) | 5/34 (15) | 1/23 (4) | 7/101 (7) |
| Physical signs | |||||
| Cyanosis | 7/10 (70) | 3/26 (11.5) | ns | ns | 10/36 (28) |
| Crackles | <50% | 17/26 (65) | 5/9 (56) | 13/23 (57) | 35/58 (60) |
| Clubbing | 5/9 (55.5)# | 12/26 (46) | 15/36 (42)# | 6/23 (26) | 38/94 (40) |
Data are presented as n/N (%), unless otherwise stated. ns: not specified. #: clubbing sometimes disappeared after steroid therapy.