Background/Purpose: Approximately 6% of adults with idiopathic inflammatory myopathy (IIM) develop Pneumocystis jirovecii pneumonia (PJP), and PJP confers higher mortality in IIM patients compared to other connective tissue diseases. There are few studies examining PJP in juvenile IIM (JIIM). Our purpose was to characterize the clinical features associated with PJP infections in JIIM.

Methods: An electronic REDCap survey of 215 questions regarding JIIM disease course, medication usage, and PJP infection was sent to members of the Pediatric Rheumatology Bulletin Board, an electronic list-serv, and members of the Childhood Arthritis and Rheumatology Research Alliance. Retrospective chart review of JIIM patients who developed PJP was completed by the primary treating physician.

Results: Survey data were completed for nine juvenile dermatomyositis and one juvenile polymyositis patients who developed PJP infection between ages 1.7-18 years. Of these, 6/10 were male and the median age of IIM disease onset was 5.9 years (range 1.6-17.2 years).  At IIM disease onset, 9/10 had weakness, 8/10 had Gottron’s papules or heliotrope rash, 6/10 had dysphonia, and 5/10 had skin ulcers. Myositis specific autoantibodies (MSA) were obtained in 9 patients: 4 were positive for anti-MDA5, 1 was positive for anti-p155/140, and 4 were MSA negative. Anti-Ro (SSA) autoantibodies were present in 5/9 patients. The median duration from IIM onset to PJP diagnosis was 3.7 months (IQR 1.7-6.9 months). At PJP diagnosis, IIM disease severity was moderate in 7/10 and severe in 2/10 patients. At the time of PJP infection, 2 patients had interstitial lung disease, one of whom also had pulmonary hypertension. The average white blood cell count at PJP diagnosis was 12.7 thousand cells/µl and 3/10 patients had a low absolute lymphocyte count (range 76-590 cells/µl). Symptoms at PJP presentation included dyspnea on exertion (10/10), hypoxia (9/10), fever (8/10), cough (8/10), and tachycardia (8/10). Mean time from symptom onset to initiation of treatment for PJP was 1 week. The average daily dose of oral prednisone was 30mg (1.1 mg/kg/day) with 8/10 patients on ≥20mg prednisone daily, and 7/10 receiving IV pulse steroids the month prior. Only 2 patients received cyclophosphamide and/or rituximab prior to PJP. Eight patients required ICU admission and 6/10 required mechanical ventilation for an average of 49 days. Two patients required extracorporeal membrane oxygenation, both of whom died secondary to complications of PJP infection. None of the patients had received PJP prophylaxis prior to infection.

Conclusion: PJP affects JIIM patients receiving systemic immunosuppression.  Most patients with PJP had moderate to severe disease at diagnosis. Skin ulcerations and anti-MDA5 autoantibodies were commonly reported.  Infection with PJP occurred in the first 6 months of disease in the majority of patients, and most patients were receiving high doses of prednisone (≥20 mg) and IV pulse steroids.  Due to the high mortality associated with PJP, prophylaxis may be warranted in a subset of JIIM patients with these disease features, especially early in the disease course when higher doses of steroids are required to control disease.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/features-of-pneumocystis-jirovecii-pneumonia-in-juvenile-idiopathic-inflammatory-myopathy/