Objective: Pneumonia due to Pneumocystis carinii has been increasingly reported in patients with connective tissue diseases, but the frequency of this complication is not known. We sought to determine the frequency of P carinii pneumonia (PCP) in patients with connective tissue diseases, and to determine the role that a hospital's acquired immunodeficiency syndrome (AIDS)-related experience may have in the diagnosis of PCP in these patients.
Methods: We used a state hospitalization registry to identify all patients with PCP and either rheumatoid arthritis, systemic lupus erythematosus, Wegener's granulomatosis, polymyositis, dermatomyositis, polyarteritis nodosa, or scleroderma who had an emergent or urgent hospitalization in California from 1983 to 1994. We compared patient and hospital characteristics between these patients and patients with connective tissue diseases hospitalized with other types of pneumonia.
Results: Two hundred twenty-three patients with connective tissue diseases were diagnosed with PCP in the 12-year study period. The frequency of PCP ranged from 89 cases/10,000 hospitalizations/year in patients with Wegener's granulomatosis to 2 cases/10,000 hospitalizations/year in patients with rheumatoid arthritis. Compared with 5,457 patients with connective tissue diseases and pneumonia due to other organisms, patients with PCP were more likely to be younger, to be male, to have private medical insurance, and to have systemic lupus erythematosus, Wegener's granulomatosis, inflammatory myopathy, or polyarteritis nodosa rather than rheumatoid arthritis, and were less likely to be African American. Hospital size, teaching status, urban/rural location, proportion of admissions due to AIDS or PCP, and proportion of patients with pneumonia undergoing bronchoscopy were each associated with the likelihood of diagnosis of PCP in univariate analyses, but only the number of patients with PCP being treated at a hospital (odds ratio [OR] 1.03 for each additional 10 cases/year, 95% confidence interval [95% CI] 1.01-1.05) was associated with the likelihood of diagnosis of PCP in multivariate analyses. Patients were also somewhat more likely to be diagnosed with PCP if there had previously been a case of PCP in a patient with a connective tissue disease at the same hospital (OR 135, 95% CI 0.98-1.85). In-hospital mortality was 45.7%, and was unrelated to hospital characteristics.
Conclusion: PCP is an uncommon, but often fatal, occurrence in patients with connective tissue disease. A hospital's prior experience with patients with PCP is associated with the likelihood that this condition is diagnosed in patients with connective tissue diseases who present with pneumonia, suggesting that diagnostic suspicion is an important factor in the correct identification of affected patients.