[Clinical analysis of pneumomediastinum complicated in polymyositis and dermatomyositis].

Objective: To analyze the clinical features of pneumomediastinum complicated in polymyositis and dermatomyositis (PM/DM) and to study the pathogenesis thereof.

Methods: The clinical data of 4 patients with pneumomediastinum complicated in dermatomyositis out of 447 PM/DM patients hospitalized in Peking Union Medical College (PUMC) Hospital Jan 1989 to June 2005, were analyzed. The records of patients with PM/DM available in English throughout the world were reviewed to collect those with pneumomediastinum as a complication. And the data of these patients were analyzed, focusing mainly on the age, gender, peak of serum creatine kinase (CK), presence of pneumomediastinum, cutaneous vasculopathy, chest radiographic changes, tracheal cannula, management, and outcome.

Results: Among the 447 patients with PM/DM hospitalized in PUMC Hospital, 134 males and 313 females, aged 42 +/- 17, pneumomediastinum was observed as a complication in four patients, 3 males and 1 female, aged 12 - 43, with a prevalence rate of 0.9%. Together with 17 cases reported in the English literatures there were 21 patients with pneumomediastinum complicated in polymyositis and dermatomyositis (PM/DM in all. Only one of the literatures reported a prevalence rate as high as 8.3% (4/48), and other literatures were merely case reports. Compared with the PM/DM patients without pneumomediastinum the mean age of the PM/DM patients with pneumomediastinum was significantly younger (34:42, P < 0.01), the male: female ratio significantly higher (13:8 to 132:311, P < 0.01), the morbidity rates of interstitial lung disease and of cutaneous vasculopathy significantly higher (18/21 to 134/443, and 12/21 to 44/443, both P < 0.01). Although statistic analysis could not be undertaken because of the peak of CK not being provided in details in the literatures, the CK levels of the patients with pneumomediastinum were mostly normal or mildly higher with a peak lower than 500 U/L Three of the 4 patients with pneumomediastinum hospitalized in PUMC Hospital and 5 of the 443 patients (1.1%) without this complication received tracheal cannula. There was a significant association of pneumomediastinum with tracheal cannula (P = 0.000).

Conclusion: Vasculopathy is strongly suspected as being responsible for the pneumomediastinum in DM, and male gender, younger age, interstitial lung disease, and tracheal cannula may be the risk factors of this pneumomediastinum complicated in PM/DM.