CLINICAL PRESENTATION AND DIAGNOSIS OF INVASIVE MOLD DISEASE IN CHILDREN

George R Thompson, III, MD: Prophylaxis has just really allowed some of these very intensive chemotherapy regimens to continue while reducing the patient’s risk for invasive mold infections or even for Candida spp. Unfortunately, though, some of these patients still do develop aspergillosis or other invasive mold infections. I think one of the things that comes up is the clinical presentation of aspergillosis in children. Does it present similarly as in adults, or do you see more dissemination? Do you see more brain or sinus disease? Any thoughts on that?

Antonio Arrieta, MD: The lung is the primary site of infection, so that’s similar to adults. But what is interesting is that the radiological imaging of the lung is significantly different than in adults. We often see nondescript changes such as multiple micronodules and fluffy nodules, less commonly the typical findings seen in adults, such as the air crescent sign and cavitated macronodules.6 But we do see multi-organ involvement with some frequency. Lung plus brain is the most common pattern for multi-organ involvement. We also see sinus involvement.1,9 Many experts recommend that once there is proven or probable aspergillosis, you should image the brain.1 We follow that strategy. As you know, mucormycosis has a significantly different pattern than invasive pulmonary aspergillosis. It’s associated with a higher frequency of lobar pneumonias and pleural effusions; rhino-orbital involvement is a common and serious presentation.1,6,21

George R Thompson, III, MD: Hats off to you that you’ve been able to get imaging of the brain in patients with pulmonary aspergillosis. We’ve tried to do that in the adult population based on reports of some cases in the literature,22 and it’s been a real challenge. There are just insurance issues, lots of logistic issues that have prevented us from doing that for all patients. But that’s tremendous to hear since the diagnostic approach to these patients can be a real challenge. We can’t always do a biopsy for these patients. We can’t always have a bronchoalveolar lavage because of thrombocytopenia or other reasons. And then we have a number of tests available, and there’s some new tests such as cell-free DNA testing, etc. What’s your general approach for diagnostics for invasive mold infections?

Antonio Arrieta, MD: Once again, it’s very patient-risk dependent. For example, if we have a young patient with AML who has persistent unexplained fever for 5 days on broad-spectrum antibiotics, we rapidly go to a high-resolution computed tomography (CT) scan of the chest. Abdominal pain is common in these patients for different reasons not associated with fungal infection, but frequently, in these patients, we end up doing CT chest and abdomen. Depending on the findings of CT chest, we will order invasive studies such as bronchoscopy if there are infiltrates on CT chest or even nodules. But often the nodules are so small that you can’t biopsy them. But, if there is a lower infiltrate or a large nodule, we tend to be aggressive with the biopsy. We like to culture our fungus if we can. We want to see the species; we like to see the susceptibility.1

Although the current recommendation based on recent data suggests that the galactomannan is not of great value for our patients receiving mold-active prophylaxis, we do follow galactomannan on these patients nevertheless.1 We do not follow 1,3-Beta-D- Glucan pre-emptively, but these assay may prove useful when fungal infection is suspected.1 If fever persists and workup is negative, then we typically proceed to cell-free DNA next-generation sequencing (NGS).1 I think it’s very important to highlight that this test is not as sensitive as people would like it to be. Particularly when it comes to Aspergillus, the sensitivity is no greater than 40%-45%.23 When it comes to non-Aspergillus molds, it goes up to around 80-90%.23 So, when we have a negative workup, we send NGS, which has been proven to be quite useful for us. When safe, we do bronchoscopy and when possible, we obtain tissue from biopsies and send these specimens for fungal polymerase chain reaction (PCR) test for Aspergillus, Mucor and other pathogens such as Nocardia spp. or Pneumocystis jirovecii. When high-resolution CT or clinical findings are supportive, we obtain fungal blood cultures looking for Fusarium spp. and sometimes for less common yeasts like Trichosporon asahii. So, the workup is pretty aggressive. Also, I forgot to mention, if the patient’s fever had resolved, but while on treatment with antibiotics the patient develops secondary fever, that also rapidly triggers workup for an invasive mold infection.

George R Thompson, III, MD: Thank you so much. That was fantastic. You mentioned the importance of trying to obtain the culture. That’s often overlooked. It’s essential to know the organism to the species level and then hopefully be able to do susceptibility testing. There’s lots of caveats with that, but we generally want to make sure we’re not treating a resistant Aspergillus infection or some other unrecognized organism. And then even with the patients who can undergo biopsy, if we see fungal structures microscopically, pathology often will tell us this is Aspergillus, but that doesn’t mean it is right. It could be Aspergillus; it could be Fusarium; it could be Scedosporium with those hyaline molds, given acute-angle branching (See Figure 3). Even specimens that look like Mucorales are sometimes wrong. They could still be Aspergillus but look pathologically like Mucorales. So, I really appreciate you emphasizing the attempt to get a positive culture—that’s so helpful moving forward.

But I wanted to circle back to the use of next-generation sequencing. That’s being used at increasing frequency. Lots of places are doing that. For some of our patients here, our pediatric colleagues have, even in these culture-negative cases where we really can’t reach a diagnosis, they’ve sent sequential samples every day or every couple of days trying to find out what’s going on and had some success with that. Anything else you want to add based on your experience with NGS?

Figure 3. Hyphal morphology associated with mucormycosis vs aspergillosis. A. Pythium insidiosum, a form of mycormycosis, Gridley stain. B. Aspergillus fumigatus, 500x, Periodic Acid Schiff stain..

A image courtesy of CDC, Lucille K. Georg. B image courtesy of CDC, William Kaplan.

Note acute angle branching.

Antonio Arrieta, MD: A negative result doesn’t mean that there is no fungal infection. So, the value of NGS is when it guides us in identifying the fungus all the way to the species level. At least here, when we have a positive NGS test, we still try to get cultures. We believe strongly that we ought to identify the species by culture, and we ought to perform susceptibility testing. I am very happy that we are not experiencing what our European colleagues are experiencing, particularly in Northern Europe, Netherlands, Germany, etc, where they are seeing widespread resistant Aspergillus fumigatus, perhaps in association with azoles used in their environmental fumigation programs. But I would hate to find out that one of my patients had one of these mutations only because they failed treatment.24 So, we are very aggressive in trying to recover the fungus. Of course, we’re not going to perform risky biopsies, but when there is accessible tissue and/or bronchoscopy is needed to obtain material, we try to perform culture wherever possible to supplement the findings of next-generation sequencing.

One thing I would like to comment on is that we were among the pioneers in using NGS to monitor success of our treatment.25 More importantly, it’s helpful to evaluate treatment failure, so we can either rapidly switch regimens or increase dosages. So, it is very reassuring when you start with a positive NGS with several thousand DNA copies, you put your patient on treatment, and 7–10 days later you repeat the test and now it has dropped to a few hundred DNA copies, and then 2–3 weeks later you don’t find it anymore. You still have the radiological findings. You’re still going to continue to treat, but it’s very reassuring to know that your NGS test has either gone down substantially or it has now become negative.

TABLE OF CONTENTS

Faculty

George R. Thompson, III, MD

Professor of Medicine
University of California, Davis, School of Medicine
Sacramento, California

Antonio C. Arrieta, MD

Division Chief
Pediatric Infectious Diseases
Children’s Hospital of Orange County (CHOC)
Orange, California

MyCARE thanks Astellas for sponsoring this activity.

Copyright © 2025. ALL RIGHTS RESERVED. MyCARE Foundation. Astellas-sponsored, MA-MM-14973. May 2025. ASTELLAS and the Flying Star Logo are registered trademarks of Astellas Pharma Inc. Used with permission.