Pemphigus and hematologic malignancies: A population-based study of 11,859 patients

Background: The association of nonparaneoplastic pemphigus with comorbid hematologic malignancies has yet to be established. Objective: To estimate the association between pemphigus and the common types of hematologic malignancies. Methods: A cross-sectional study was conducted comparing pemphigus patients with age-, sex- and ethnicity-matched control subjects regarding the prevalence of 6 comorbid hematologic malignancies. The study was performed using the computerized database of Clalit Health Services ensuring the availability of 4.5 million patients. Results: The study included 1985 pemphigus patients and 9874 control subjects. The prevalence of chronic leukemia (0.9% vs 0.4%, odds ratio [OR] 2.1, 95% confidence interval [CI] 1.2-3.6), multiple myeloma (0.8% vs 0.4%, OR 2.2, 95% CI 1.2-3.9), and non-Hodgkin lymphoma (1.8% vs 1.2%, OR 1.5, 95% CI 1.0-2.2) was greater in patients with pemphigus than in controls. The association with chronic leukemia remained significant following the adjustment for immunosuppressive therapy (adjusted OR 2.0, 95% CI 1.1-3.7). No significant associations were observed between pemphigus and acute leukemia, Hodgkin lymphoma, myelodysplastic syndrome, and polycythemia vera. Limitations: Lack of immunopathologic validation of the diagnosis of pemphigus. Conclusion: A significant association was observed between pemphigus and chronic leukemia, multiple myeloma, and non-Hodgkin lymphoma. Further research is warranted to establish this observation in other cohorts.