Determining the incidence of Pneumocystis pneumonia in patients with autoimmune blistering diseases not receiving routine prophylaxis

IMPORTANCE: Pneumocystis pneumonia (PCP) is a potentially lethal opportunistic infection that primary prophylaxis can help prevent. The risk of prophylactic therapy must be weighed against the incidence of PCP in the patient population. Prophylaxis most frequently involves trimethoprim-sulfamethoxazole, with second-line therapies, including atovaquone, dapsone, and pentamide. The indication for prophylaxis in immunocompromised patients without HIV is less well defined. Previously, an incidence of at least 3.5% has been proposed as a cutoff to justify prophylaxis. OBJECTIVE: To assess the incidence of PCP in patients with autoimmune blistering diseases receiving no routine prophylaxis. DESIGN, SETTING, AND PARTICIPANTS: This was a retrospective analysis of patient medical records to determine the incidence of PCP infections. The multicenter study was performed at tertiary care centers that provide care for patients with autoimmune blistering disease in Germany, Italy, Singapore, Israel, and the Netherlands. Patients had a confirmed diagnosis of pemphigus vulgaris/foliaceus, bullous pemphigoid, epidermolysis bullosa acquisita, mucous membrane pemphigoid/cicatricial pemphigoid, or anti-p200 pemphigoid. MAIN OUTCOMES AND MEASURES: To determine the incidence of PCP defined as patients with the International Classification of Diseases, Ninth Revision (ICD-9), code 136.3, for PCP, or free text documentation of PCP occurring based on characteristic radiographic findings with elevated lactate dehydrogenase, or hospitalization for pneumonia with bronchioalveolar lavage demonstrating Pneumocystis jiroveci on confirmatory stains. RESULTS: A total of 801 patients with autoimmune blistering diseases were included in this study; their mean (SD) age was 66.5 (17.6) years, and a total of 465 (58%) were female. Only 1 patient developed PCP, resulting in an incidence rate of 0.1%. This incidence significantly fell below the recommended threshold of 3.5% (0.1% vs 3.5%, χ12= 27.0; P < .001). This incidence was significantly lower than the previously reported incidence of PCP in all immunosuppressed dermatologic patients (0.1% vs 1.3%; χ12= 8.2; P = .004). CONCLUSIONS AND RELEVANCE: Routine Pneumocystis prophylaxis for patients with autoimmune blistering diseases does not seem to be warranted. Patients with autoimmune blistering disease seem to have a lower risk of PCP than the general population of immunosuppressed dermatology patients. Risks of routine prophylaxis include hyperkalemia, hypoglycemia, photosensitivity, thrombocytopenia, and more rare adverse reactions.