IMPORTANCE The association between pemphigus and neurologic diseases was not evaluated systematically in the past. In a recent uncontrolled cross-sectional study, Parkinson disease was found to be significantly associated with pemphigus; in the same study, epilepsy had a nonsignificant association with pemphigus. Several case reports have suggested that pemphigus coexists with multiple sclerosis and dementia. OBJECTIVE To estimate the association between pemphigus and 4 neurologic conditions (dementia, epilepsy, Parkinson disease, and multiple sclerosis), using one of the largest cohorts of patients with pemphigus. DESIGN, SETTING, AND PARTICIPANTS A retrospective population-based cross-sectional study was performed between January 1, 2004, and December 31, 2014, using the database of Clalit Health Services, the largest public health care organization in Israel, in the setting of general community clinics, primary care and referral centers, and ambulatory and hospitalized care. A total of 1985 patients with a new diagnosis of pemphigus and 9874 controls were included in the study. MAIN OUTCOMES AND MEASURES The proportion of dementia, epilepsy, Parkinson disease, and multiple sclerosis was compared between patients diagnosed with pemphigus and age-, sex-, and ethnicity-matched control participants. Logistic regression was used to calculate odds ratios (ORs) for dementia, epilepsy, Parkinson disease, and multiple sclerosis. The association was examined after a sensitivity analysis that included only patients treated with long-term, pemphigus-specific medications (corticosteroids, immunosuppressants, or rituximab) and after adjustment for several confounding factors. RESULTS When comparing the 1985 cases (1188 women and 797 men; mean [SD] age, 72.1 [18.5] years) with the 9874 controls (5912 women and 3962 men; mean [SD] age, 72.1 [18.5] years), dementia was seen in 622 cases (31.3%) vs 1856 controls (18.8%), with an OR of 1.97 (95%CI, 1.77-2.20). Epilepsy was present in 74 cases (3.7%) vs 210 controls (2.1%), with an OR of 1.78 (95%CI, 1.36-2.33). Parkinson disease was seen in 175 cases (8.8%) vs 437 controls (4.4%), with an OR of 2.09 (95%CI, 1.74-2.51). Multiple sclerosis was present in 2 cases (0.1%) vs 6 controls (0.01%), with an OR of 1.65 (95%CI, 0.34-8.22). Study findings were robust to sensitivity analysis that included patients receiving pemphigus-specific treatments. Estimates were not altered significantly after controlling for comorbidities and overuse of health care. CONCLUSIONS AND RELEVANCE An associationwas observed between pemphigus and specific neurologic diseases, including dementia, Parkinson disease, and epilepsy. Physicians treating patients with pemphigus should be aware of this possible association. Patients with pemphigus should be carefully assessed for comorbid neurologic disorders and receive appropriate treatment.