Clinical Topics

Fatal Drug-Resistant Invasive Pulmonary Aspergillus fumigatus in a 56-Year-Old Immunosuppressed Man

Immune status, severity or burden of disease, appropriate dosing of medication, and drug resistance are important considerations when treating immunosuppressed patients.

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References

Historically, aspergillosis in patients with hematopoietic stem cell transplantation (HSCT) has carried a high mortality rate. However, recent data demonstrate a dramatic improvement in outcomes for patients with HSCT: 90-day survival increased from 22% before 2000 to 45% over the past 15 years.1 Improved outcomes coincide with changes in transplant immunosuppression practices, use of cross-sectional imaging for early disease identification, galactomannan screening, and the development of novel treatment options.

Voriconazole is an azole drug that blocks the synthesis of ergosterol, a vital component of the cellular membrane of fungi. Voriconazole was approved in 2002 after a clinical trial demonstrated an improvement in 50% of patients with invasive aspergillosis in the voriconazole arm vs 30% in the amphotericin B arm at 12 weeks.2 Amphotericin B is a polyene antifungal drug that binds with ergosterol, creating leaks in the cell membrane that lead to cellular demise. Voriconazole quickly became the first-line therapy for invasive aspergillosis and is recommended by both the Infectious Disease Society of American (IDSA) and the European Conference on Infections in Leukemia.3

Case Presentation

A 55-year-old man with high-risk chronic myelogenous leukemia (CML) underwent a 10 of 10 human leukocyte antigen allele and antigen-matched peripheral blood allogeneic HSCT with a myeloablative-conditioning regimen of busulfan and cyclophosphamide, along with prophylactic voriconazole, sulfamethoxazole/trimethoprim, and acyclovir. After successful engraftment (without significant neutropenia), his posttransplant course was complicated by grade 2 graft vs host disease (GVHD) of the skin, eyes, and liver, which responded well to steroids and tacrolimus. Voriconazole was continued for 5 months until immunosuppression was minimized (tacrolimus 1 mg twice daily). Two months later, the patient’s GVHD worsened, necessitating treatment at an outside hospital with high-dose prednisone (2 mg/kg/d) and cyclosporine (300 mg twice daily). Voriconazole prophylaxis was not reinitiated at that time.

One year later, at a routine follow-up appointment, the patient endorsed several weeks of malaise, weight loss, and nonproductive cough. The patient’s immunosuppression recently had been reduced to 1 mg/kg/d of prednisone and 100 mg of cyclosporine twice daily. A chest X-ray demonstrated multiple pulmonary nodules; follow-up chest computed tomography (CT) confirmed multiple nodular infiltrates with surrounding ground-glass opacities suspicious with a fungal infection (Figure 1).

Bronchoscopy with bronchoalveolar lavage (BAL) was significant for a positive Aspergillus fumigatus (A fumigatus) DNA polymerase chain reaction (PCR) assay and a BAL galactomannan level of > 5.3 optical density index (ODI) (normal, < 0.5). Bacterial and fungal cultures were negative, and serum galactomannan testing was not performed.

Treatment with oral voriconazole (300 mg twice daily) was initiated for probable pulmonary aspergillosis. Cyclosporine (150 mg twice daily) and prednisone (1 mg/kg/d) were continued throughout treatment out of concern for hepatic GVHD. The patient’s symptoms improved over the next 10 days, and follow-up chest imaging demonstrated improvement.

Two weeks after initiation of voriconazole treatment, the patient developed a new productive cough and dyspnea, associated with fevers and chills. Repeat imaging revealed right lower-lobe pneumonia. The serum voriconazole trough level was checked and was 3.1 mg/L, suggesting therapeutic dosing. The patient subsequently developed acute respiratory distress syndrome and required intubation and mechanical ventilation. Repeat BAL sampling demonstrated multidrug-resistant Escherichia coli, a BAL galactomannan level of 2.0 ODI, and negative fungal cultures. The patient’s hospital course was complicated by profound hypoxemia, requiring prone positioning and neuromuscular blockade. He was treated with meropenem and voriconazole. His immunosuppression was reduced, but he rapidly developed acute liver injury from hepatic GVHD that resolved after reinitiation of cyclosporine and prednisone at 0.75 mg/kg/d.

The patient improved over the next 3 weeks and was successfully extubated. Repeat chest CT imaging demonstrated numerous pneumatoceles in the location of previous nodules, consistent with healing necrotic fungal disease, and a new right lower-lobe cavitary mass (Figure 2). Two days after transferring out of the intensive care unit, the patient again developed hypoxemia and fevers to 39° C. Bronchoscopy with BAL of the right lower lobe revealed positive A fumigatus and Rhizopus sp polymerase chain reaction (PCR) assays, although fungal cultures were positive only for A fumigatus. Liposomal amphotericin B (5 mg/kg) was added to voriconazole therapy to treat mucormycosis and to provide a second active agent against A fumigatus.

Unfortunately, the patient’s clinical status continued to deteriorate with signs of progressive respiratory failure and infection despite empiric, broad-spectrum antibiotics and dual antifungal therapy. His serum voriconazole level continued to be therapeutic at 1.9 mg/L. The patient declined reintubation and invasive mechanical ventilation, and he ultimately transitioned to comfort measures and died with his family at the bedside.

Autopsy demonstrated widely disseminated Aspergillus infection as the cause of death, with evidence of myocardial, neural, and vascular invasion of A fumigatus (Figures 3 and 4).

Rhizopus sp was identified in the large right lower lobe cavity without signs of angioinvasion, suggestive of cavity colonization. Follow-up sensitivity data (University of Texas, San Antonio, CLSI M38 A2, broth microdilution) of the A fumigatus demonstrated voriconazole sensitivity (MIC 0.25 µg/dL) but surprisingly, amphotericin B resistance (MIC > 2 µg/dL).

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