A Case of Multifocal Necrotizing Blastomycosis Pneumonia and Acute Respiratory Distress Syndrome (ARDS) in an Adolescent with Type 1 Diabetes Mellitus

Introduction: Blastomyces species are thermally dimorphic fungi endemic to North America, especially areas bordering the Mississippi, Ohio and St. Lawrence rivers, and the Great Lakes. Blastomycosis infections are estimated to occur in 3-13% in the pediatric population. Pediatric literature for blastomycosis has been mostly limited to small studies and case series. Recent literature suggests increasing rates of infections, less morbidity and mortality as compared to adults, with asthma as the most common comorbid condition. Although pulmonary disease is the most common presentation, it rarely progresses to acute respiratory distress syndrome (ARDS).

Case Description: A 17-year-old female, living in the Chicago area, and with type 1 diabetes mellitus and childhood asthma, presented to the emergency room with acute hypoxemic respiratory failure after 14 days of cough, dyspnea, chest pain, and fevers as high as 105°F. Her initial radiographic imaging revealed bilateral infiltrates and consolidations in the right middle and lower lobes. She was admitted to the step down unit for further care. A respiratory viral panel, including COVID-19 evaluation, was negative. She was started on low-flow nasal cannula, ceftriaxone, azithromycin, albuterol, and maintenance IV fluids. On hospital day 2, she was transferred to the pediatric intensive care unit for worsening respiratory distress and escalated to high-flow nasal cannula. She was treated empirically for presumed bacterial pneumonia with ceftriaxone (7-day course), azithromycin (5-day course), cefepime (5-day course), clindamycin (2-day course), and vancomycin (14-day course). Despite this treatment, repeat chest imaging showed worsening disease and she required escalation to BiPAP for progression of her ARDS and impending respiratory failure. Karius testing results indicated Blastomyces dermatitidis at low levels typically not clinically relevant. Sputum and bronchoalveolar lavage cultures demonstrated no significant pathogenic bacteria. Pathology exam of the biopsy obtained from bronchoscopy was consistent with Blastomyces. Urine antigen test was positive for both Blastomyces and Histoplasma. She clinically improved after initiating Amphotericin B lipid complex (6-day course), with transition to oral itraconazole and adjunctive therapy with IV methylprednisolone. She was discharged home after a 30-day hospital stay.

Discussion: Pulmonary blastomycosis presents with a broad variety of signs and symptoms. Timely diagnosis is challenging. Pulmonary blastomycosis has no pathognomonic radiographic patterns. Severe acute pulmonary infection that fails to respond to antibacterial treatment should prompt investigation for fungal infection, including urine antigen tests for Histoplasma and Blastomyces, serum galactomannan, beta-1,3-D-glucan, and next-generation sequencing of microbial cell-free DNA (eg, Karius test). Close respiratory monitoring should occur in a pediatric intensive care unit.

Conclusion: Blastomycosis is not typically in the initial differential diagnosis unless the patient has other clinical findings, fails to improve on antibacterial therapy, or has identified risk factors for exposure. Failure of prompt recognition is associated with poor outcomes, increased morbidity and mortality, increased length of hospital stay, and cost.