Aspergillosis
- Overview
- Epidemiology
- Pathophysiology
- Clinical Forms
- Diagnosis
- Treatment
- Complications
- Prognosis
- Prevention
- Recent Research
- References
- Featured Videos
1. Overview
Aspergillosis encompasses a broad spectrum of diseases caused by molds of the genus Aspergillus, ubiquitous environmental fungi found in soil, decaying vegetation, and organic material worldwide. Over 300 species exist, but a handful are responsible for the vast majority of human disease. Aspergillus fumigatus is by far the most important pathogen: it is thermotolerant (grows at body temperature 37°C and beyond), produces small conidia of only 2–3 micrometers in diameter that are ideally sized to bypass upper airway defenses and penetrate deep into pulmonary alveoli, and possesses a suite of virulence factors including gliotoxin (an immunosuppressive mycotoxin), siderophores for iron acquisition, and a robust cell wall that resists phagocytic digestion. Aspergillus flavus is the second most clinically significant species; it produces aflatoxin, a potent hepatocarcinogen, and is disproportionately responsible for sinusitis and cutaneous infections, particularly in transplant recipients and immunocompromised patients in tropical and subtropical regions. Aspergillus niger is the most common cause of otomycosis (fungal ear canal infection) and is also implicated in rare cases of pulmonary disease. Aspergillus terreus is noteworthy for its intrinsic resistance to amphotericin B, complicating treatment of the small proportion of invasive infections it causes.
The clinical spectrum of aspergillosis is remarkably wide and is determined almost entirely by the immune status and pulmonary architecture of the host. In individuals with intact immunity, inhaled conidia are cleared efficiently and cause no disease. In atopic individuals with asthma or cystic fibrosis, sensitization to Aspergillus antigens drives a hypersensitivity syndrome called allergic bronchopulmonary aspergillosis (ABPA), which can cause recurrent pulmonary infiltrates, mucous plugging, and ultimately bronchiectasis if untreated. In patients with pre-existing pulmonary cavities — most commonly residual tuberculosis cavities — the fungus colonizes the dead space and forms a fungal ball (aspergilloma) that is locally destructive and prone to causing hemoptysis. Chronic pulmonary aspergillosis (CPA) describes a semi-invasive form occurring in patients with mild immune deficiency or structural lung disease, where cavitation progresses over months to years. Finally, and most lethally, invasive pulmonary aspergillosis (IPA) occurs when the fungus germinates, invades pulmonary vasculature, and disseminates in profoundly immunosuppressed hosts, with untreated mortality approaching 100%.
2. Epidemiology
Aspergillus conidia are genuinely ubiquitous: outdoor air typically contains 1–100 conidia per cubic meter, with concentrations rising dramatically near construction sites, compost heaps, and soil disturbance events. Indoor environments can harbor even higher concentrations if ventilation systems are contaminated or if there is water damage and mold growth. Every person inhales hundreds to thousands of conidia daily, yet disease is uncommon in immunocompetent individuals, underscoring how effectively the healthy immune system clears these particles.
The incidence of invasive aspergillosis has risen substantially over the past three decades, driven by expansion of the immunosuppressed population. An estimated 200,000–300,000 cases of IPA occur annually worldwide, with case fatality rates ranging from 30% in optimally treated neutropenic patients to over 90% in patients with cerebral dissemination. The highest-risk populations are those undergoing allogeneic hematopoietic stem cell transplantation (HSCT), particularly in the early engraftment period and during treatment of graft-versus-host disease (GVHD) with high-dose corticosteroids; patients receiving induction chemotherapy for acute myeloid leukemia (AML) with prolonged neutropenia; solid organ transplant recipients (lung transplant carries the greatest risk); and patients receiving prolonged high-dose corticosteroids for any indication. COVID-19-associated pulmonary aspergillosis (CAPA) emerged as a recognized entity during the pandemic, particularly in mechanically ventilated ICU patients.
ABPA affects approximately 1–2% of all asthma patients and 7–35% of patients with cystic fibrosis, though exact figures vary by diagnostic criteria applied and population studied. Aspergilloma occurs wherever the underlying structural lung diseases — primarily pulmonary tuberculosis and sarcoidosis — are prevalent, making it particularly common in high TB-burden regions of sub-Saharan Africa, Southeast Asia, and South Asia. Chronic pulmonary aspergillosis affects an estimated 3 million people worldwide and is substantially underdiagnosed because its presentation overlaps with reactivation tuberculosis, COPD exacerbations, and lung cancer.
3. Pathophysiology
The outcome of Aspergillus inhalation depends on a dynamic interplay between the quantity and virulence of the inhaled inoculum and the efficiency of host defense mechanisms. In immunocompetent individuals, the mucociliary escalator of the conducting airways physically removes the majority of inhaled particles; conidia that reach the alveoli are recognized by pattern recognition receptors (particularly Dectin-1, TLR2, and TLR4) on alveolar macrophages, which engulf and kill them through oxidative bursts and lysosomal mechanisms. If the macrophage barrier is overwhelmed, recruited neutrophils provide a critical second line of defense through neutrophil extracellular traps (NETs) and direct hyphal killing. This two-tiered defense is why both quantitative neutrophil deficiency (neutropenia, <500/μL for >7–10 days) and qualitative neutrophil dysfunction (chronic granulomatous disease) are the most potent risk factors for IPA.
When host defenses are compromised, conidia that escape macrophage clearance germinate into hyphae. The switch from dormant conidia to actively growing hyphae is critical: hyphae are too large for phagocytosis and are the form that invades tissue. In invasive disease, hyphae penetrate pulmonary blood vessel walls — angioinvasion — producing the characteristic computed tomography finding of the halo sign: a nodule surrounded by a halo of ground-glass opacity representing perilesional hemorrhage from hyphal invasion and partial obstruction of vessel walls. This hemorrhagic halo is present early (within the first 72 hours of lesion formation) before infarction is complete, representing an important diagnostic window. As infarction proceeds over days to weeks, the necrotic center liquefies and separates, producing the air crescent sign — a crescent of air surrounding a contracting nodule — which paradoxically indicates neutrophil recovery (improved host killing of fungal tissue) and is therefore a sign of improving disease despite its dramatic appearance.
Virulence factors beyond thermotolerance are crucial. Siderophores (triacetylfusarinine C and ferricrocin) scavenge iron from the host environment, which is essential for fungal growth and hyphal extension. Gliotoxin suppresses macrophage and neutrophil function, allowing fungal survival in partially immunocompetent hosts. The hydrophobic rodlet layer of the conidial surface prevents phagocytic recognition by masking pathogen-associated molecular patterns. In ABPA, the pathophysiology is immunological rather than invasive: sensitized airway mast cells release histamine and leukotrienes upon Aspergillus antigen exposure (type I hypersensitivity, IgE-mediated), while immune complexes deposited in bronchial walls activate complement and recruit eosinophils and neutrophils (type III hypersensitivity, IgG-mediated). This combined airway inflammation impairs mucociliary clearance, promotes mucous plug formation with central bronchiectasis, and if untreated culminates in fibrotic lung disease. A key morphological clue distinguishing Aspergillus hyphae from Mucor (the other major mold pathogen) is branching angle: Aspergillus hyphae branch at 45° with regular septa, while mucormycetes branch at 90° with pauciseptate ribbon-like hyphae.
4. Clinical Forms
Allergic Bronchopulmonary Aspergillosis (ABPA)
ABPA occurs in patients with pre-existing asthma or cystic fibrosis who become sensitized to Aspergillus antigens. The clinical presentation includes recurrent episodes of wheezing and breathlessness that are poorly controlled with standard bronchodilator therapy, expectoration of characteristic brownish-black or greenish mucous plugs representing casts of obstructed bronchi, and transient or fleeting pulmonary infiltrates visible on chest imaging. Low-grade fever and peripheral blood eosinophilia are common. The Rosenberg-Patterson diagnostic criteria require all of the following: underlying asthma or cystic fibrosis; positive immediate skin test wheal-and-flare reaction to Aspergillus fumigatus antigen; elevated total serum IgE (typically >1000 IU/mL, though lower thresholds are used in CF patients); elevated Aspergillus-specific IgE (>0.35 kUA/L); precipitating IgG antibodies against Aspergillus; and central (proximal) bronchiectasis on high-resolution CT — the classical "finger-in-glove" appearance of mucus-filled dilated bronchi. Peripheral eosinophilia >500/μL and a history of brown mucous plug expectoration strongly support the diagnosis. Disease staging follows the Rosenberg-Patterson classification: Stage I (acute), Stage II (remission), Stage III (exacerbation with IgE doubling from remission), Stage IV (corticosteroid-dependent asthma), and Stage V (end-stage fibrotic lung disease). Treatment combines oral corticosteroids (prednisolone 0.5 mg/kg/day tapered over months) to suppress the inflammatory response with itraconazole (200 mg twice daily) as an antifungal steroid-sparing agent that reduces fungal burden. Voriconazole is used as an alternative. In patients with refractory or steroid-dependent disease, omalizumab (anti-IgE monoclonal antibody) has demonstrated efficacy in reducing exacerbation frequency and steroid requirements. Total serum IgE is used to monitor treatment response — a falling IgE indicates remission, while a doubling from the remission baseline signals exacerbation.
Aspergilloma
An aspergilloma (fungal ball or mycetoma) forms when Aspergillus colonizes a pre-existing pulmonary cavity without significant tissue invasion. The most common underlying cavities result from previous pulmonary tuberculosis (the leading cause worldwide), bullous emphysema, pulmonary sarcoidosis, bronchiectasis, prior lung abscess, and ankylosing spondylitis with pulmonary apical fibrosis. The fungal ball consists of a tangled mass of hyphae, mucus, cellular debris, and fibrin that sits within the cavity, mobile on decubitus positioning. The pathognomonic CT finding is the air crescent sign — an air-filled crescent surrounding a mobile soft-tissue mass within a cavity — and a freely mobile intracavitary mass that shifts with patient positioning (the "rolling ball" or dependent position sign). Most aspergillomas are asymptomatic and discovered incidentally on chest imaging. Hemoptysis occurs in 50–80% of cases over the lifetime of the lesion, ranging from mild blood-streaking of sputum to massive, life-threatening hemorrhage from erosion of bronchial arteries or direct invasion of vascular structures adjacent to the cavity wall. Systemic invasive disease is uncommon because the fungus is essentially contained within the cavity, but local invasion (semi-invasive or chronic pulmonary aspergillosis) can occur, particularly if the patient's immunity wanes. Management is guided by symptoms: asymptomatic aspergillomas may be observed with serial imaging. Massive hemoptysis (>300–600 mL/24h) requires emergency bronchial artery embolization, which controls hemorrhage in 70–85% of cases but has a recurrence rate of 20–30% at one year. Surgical resection (lobectomy or pneumonectomy) is the only curative option for accessible lesions and adequate pulmonary reserve, but perioperative morbidity is substantial, particularly with adherent pleura and poor underlying lung function.
Chronic Pulmonary Aspergillosis (CPA)
CPA represents a semi-invasive form of aspergillosis occurring over months to years in patients who are mildly immunosuppressed or have underlying structural lung disease but do not have the profound immunosuppression that characterizes invasive disease. Risk factors include prior or current pulmonary tuberculosis, non-tuberculous mycobacterial (NTM) infection, COPD, pulmonary sarcoidosis, and prior treated IPA. The clinical presentation is insidious: progressive fatigue, weight loss, night sweats, chronic productive cough, and hemoptysis developing over a period of months to years, closely mimicking reactivation tuberculosis or lung cancer. CT imaging reveals progressive upper lobe cavitation with thickened cavity walls, new nodules forming within or adjacent to cavities, adjacent pleural thickening, and in some cases a fungal ball within the cavity (chronic cavitary pulmonary aspergillosis, CCPA). Elevated serum Aspergillus-specific IgG is the most reliable laboratory marker, found in 90% of CPA patients; this distinguishes CPA from simple aspergilloma (IgG elevated) versus colonization (IgG usually lower). Galactomannan is frequently negative in CPA because the disease is not angioinvasive. Treatment requires long-term oral antifungal therapy, typically itraconazole 200 mg twice daily or voriconazole 200 mg twice daily for a minimum of six months and often for several years; many patients require indefinite suppressive therapy because relapse on treatment cessation is common. Surgical resection of localized accessible disease combined with antifungal therapy offers the best chance of cure but carries significant operative risk in patients with impaired pulmonary reserve.
Invasive Pulmonary Aspergillosis (IPA)
IPA is the most severe and rapidly fatal form, occurring in patients with severely impaired immunity who cannot contain germinating conidia. The highest-risk patient categories are those with prolonged neutropenia (absolute neutrophil count <500/μL persisting beyond 7–10 days, as occurs during induction chemotherapy for AML or conditioning regimens for HSCT); allogeneic HSCT recipients, particularly during the pre-engraftment period and during treatment of GVHD with high-dose corticosteroids; lung transplant recipients; patients receiving tumor necrosis factor (TNF) inhibitors; and patients with advanced HIV infection (CD4 <50/μL). The clinical presentation is fever persisting despite broad-spectrum antibacterial therapy in a neutropenic patient, often accompanied by pleuritic chest pain, hemoptysis, or dry cough. In non-neutropenic patients (e.g., those on corticosteroids), fever may be absent and the presentation is more insidious. CT chest is the pivotal diagnostic tool: early IPA produces multiple pulmonary nodules surrounded by ground-glass halos (halo sign, present in the first 1–3 weeks when hemorrhagic infarction is evolving); later, wedge-shaped pleural-based consolidations representing vascular infarcts become evident; the air crescent sign appears with neutrophil recovery 2–4 weeks after lesion formation. Sinusitis (especially maxillary and ethmoid), cerebral aspergillosis (brain abscesses, meningitis), cutaneous lesions, and endophthalmitis represent sites of dissemination from primary pulmonary disease or direct sinonasal extension to brain. Serum galactomannan (GM) enzyme immunoassay using a cut-off optical density index of ≥0.5 has sensitivity of 70–80% in HSCT patients and neutropenic patients but only 30–50% in SOT recipients and those on corticosteroids (false negatives). Bronchoalveolar lavage (BAL) GM using a cut-off of ≥1.0 achieves sensitivity of 75–90% and is now preferred over serum GM for early diagnosis. Beta-D-glucan is elevated in IPA but is non-specific (positive in candidiasis, PCP, and other fungal infections). Lateral flow assay for GM on urine, serum, or BAL is a point-of-care alternative. Aspergillus PCR from blood or BAL is now included in consensus diagnostic criteria and adds sensitivity when combined with GM.
5. Diagnosis
The diagnosis of aspergillosis is established using the European Organization for Research and Treatment of Cancer and the Mycoses Study Group (EORTC/MSG) consensus definitions, which classify cases as proven, probable, or possible based on the combination of host factors, clinical criteria, and mycological criteria. A proven diagnosis requires histopathological evidence of characteristic septate hyphae with 45° branching in tissue (needle core biopsy, surgical resection, or autopsy specimen) combined with a positive culture from the same site, or positive culture from a normally sterile site. In clinical practice, tissue biopsy is frequently not possible in thrombocytopenic or coagulopathic patients, making probable and possible categories most practically useful for treatment decisions.
CT of the chest is the cornerstone of IPA diagnosis. The halo sign — a nodule or mass surrounded by a zone of ground-glass opacity — is present in roughly 70–90% of neutropenic IPA patients early in the disease course and is highly suggestive of IPA (positive predictive value approximately 80% in the appropriate host). It must be distinguished from other causes of pulmonary nodules with halos, including mucormycosis, septic emboli, hemorrhagic metastases, and organizing pneumonia. The air crescent sign, while classically associated with aspergillosis, is neither sensitive nor specific and is a late finding; its appearance during neutrophil recovery should not be interpreted as worsening disease. CT of sinuses is important for detecting sinusitis, which may precede pulmonary dissemination or represent a separate focus requiring surgical debridement.
Bronchoscopy with BAL is essential when CT findings are present: BAL galactomannan (cut-off ≥1.0) and BAL Aspergillus PCR add diagnostic yield beyond serum GM alone. Culture of BAL for Aspergillus has limited sensitivity (30–50%) due to the low fungal burden in BAL relative to tissue, but positive culture from BAL has high specificity (>90%) and provides the isolate for antifungal susceptibility testing. For ABPA, the diagnostic workup centers on serology: total IgE, Aspergillus-specific IgE (ImmunoCAP), and Aspergillus-specific IgG precipitins, combined with immediate skin prick testing and high-resolution CT for central bronchiectasis. For CPA, serum Aspergillus IgG is the most diagnostically reliable test. For aspergilloma, the CT appearance is usually sufficient for a radiological diagnosis without mycological confirmation, though sputum culture positive for Aspergillus supports the diagnosis.
6. Treatment
The treatment of IPA was transformed in 2002 by the landmark NEJM trial demonstrating superiority of voriconazole over amphotericin B deoxycholate as primary therapy. Voriconazole remains the first-line treatment for IPA: intravenous loading doses of 6 mg/kg every 12 hours for two doses, followed by 4 mg/kg IV every 12 hours; the oral formulation (200 mg every 12 hours) is bioequivalent and appropriate once the patient can tolerate oral medications. Therapeutic drug monitoring is essential because voriconazole is metabolized by CYP2C19, a highly polymorphic enzyme: poor metabolizers (particularly common in Asian populations, prevalence 15–20%) achieve dramatically higher drug levels, while ultra-rapid metabolizers may have subtherapeutic levels. Target trough concentrations are 1.0–5.5 μg/mL; troughs above this range are associated with hepatotoxicity, encephalopathy, and visual hallucinations (phosphenes, photopsia), while troughs below 1.0 μg/mL predict treatment failure. Drug interactions are extensive through CYP2C19/3A4 inhibition. Isavuconazole (isavuconazonium sulfate), studied in the SECURE trial (non-inferiority to voriconazole, published Lancet 2016), has emerged as an important alternative with a more favorable safety profile: no QTc prolongation (voriconazole has mild QTc effects), no visual side effects, fewer drug interactions, and both IV and oral formulations with high bioavailability. Liposomal amphotericin B (L-AmB, 3–5 mg/kg/day IV) remains the preferred second-line agent for patients intolerant of azoles or in settings where azole resistance is suspected; conventional amphotericin B deoxycholate should not be used (nephrotoxicity without improved efficacy). Combination antifungal therapy (e.g., voriconazole plus an echinocandin) is not currently recommended as routine practice based on available evidence from clinical trials, though it may be considered in refractory or breakthrough IPA at the discretion of the treating clinician.
ABPA treatment centers on suppressing the immunological response and reducing fungal burden. Oral prednisolone (0.5 mg/kg/day) is initiated for 2 weeks and then tapered over 4–6 months, with tapering guided by total IgE levels. Itraconazole (200 mg twice daily, with food for absorption, monitoring levels) reduces Aspergillus airway burden and has demonstrated steroid-sparing effects in two randomized trials; voriconazole is an alternative for itraconazole-intolerant patients. In refractory or corticosteroid-dependent disease, omalizumab (anti-IgE, 150–600 mg SC every 2–4 weeks based on IgE level) reduces exacerbation frequency and steroid requirements in uncontrolled studies. Treatment of CPA requires prolonged oral antifungal therapy: itraconazole 200 mg twice daily or voriconazole 200 mg twice daily for at least 6 months with ongoing monitoring of liver function and drug levels; relapse rates after stopping antifungals are 40–50%, leading many experts to recommend indefinite suppressive therapy for patients with progressive disease or after IPA. Surgical resection combined with antifungal therapy can be curative in CPA patients with localized disease and adequate pulmonary reserve. Bronchial artery embolization addresses hemoptysis in aspergilloma emergently but is not a curative treatment; elective surgery for simple aspergilloma with hemoptysis carries significant risk if the underlying lung is diseased.
7. Complications
The complications of aspergillosis span a range of severity from nuisance to uniformly fatal, largely determined by the clinical form and adequacy of immune function. In IPA, angioinvasion enables hematogenous dissemination to virtually any organ. Cerebral aspergillosis — occurring in 10–20% of IPA patients — carries a mortality rate exceeding 90% even with aggressive antifungal therapy; it presents as multiple brain abscesses (CT: ring-enhancing lesions), cerebral infarctions (from vascular invasion), or meningitis, often with few early neurological signs in the neutropenic host. Spinal epidural abscess and vertebral osteomyelitis result from contiguous extension or hematogenous seeding. Endophthalmitis leads to permanent vision loss in the majority of affected eyes. Endocarditis (particularly prosthetic valve) is almost uniformly fatal without surgical valve replacement, which itself carries prohibitive risk in critically ill patients. Aspergillus cutaneous infection manifests as necrotic plaques at sites of catheter insertion or skin trauma in the immunocompromised host and is an under-recognized sign of systemic dissemination.
For aspergilloma, the most life-threatening complication is massive hemoptysis, defined as expectoration of greater than 300–600 mL of blood within 24 hours. Hemoptysis results from erosion of bronchial arteries running alongside the cavity wall or from direct hyphal penetration of adjacent vessels. Massive hemoptysis carries a mortality rate of up to 50% and requires emergency bronchial artery embolization as the initial life-saving intervention. Recurrence of hemoptysis after embolization is common (approximately 30% at 12 months) due to collateral vessel formation. A critical emerging complication is azole antifungal resistance in A. fumigatus: environmental acquisition of resistance through fungicide use in agriculture has driven the emergence of TR34/L98H and other CYP51A promoter mutations conferring resistance to itraconazole, voriconazole, and posaconazole simultaneously. Pan-azole-resistant strains have been isolated in Europe (Netherlands, UK, Denmark), South Africa, India, and other regions with intensive agricultural azole use. Infection with azole-resistant strains is associated with substantially higher mortality and requires treatment with liposomal amphotericin B or newer antifungals such as olorofim.
8. Prognosis
Prognosis in aspergillosis varies enormously by clinical form and patient characteristics. For ABPA, the outlook is generally favorable with appropriate treatment: most patients achieve clinical remission with oral corticosteroids and antifungal therapy, and progression to fibrotic lung disease (Stage V) is largely preventable with consistent treatment and monitoring. Long-term outcomes in ABPA parallel those of the underlying asthma or CF; disease-specific mortality is low when the condition is recognized and managed early.
For aspergilloma, 10-year mortality in population-based studies is primarily driven by the underlying structural lung disease (TB sequelae, COPD, sarcoidosis) rather than the aspergilloma itself. Simple aspergilloma with no or minor hemoptysis has a relatively benign course, with spontaneous lysis of the fungal ball occurring in a minority of cases. The 5-year mortality is approximately 20–30% in surgical series, largely attributable to underlying disease. The subset with recurrent or massive hemoptysis have dramatically worse outcomes without definitive treatment.
IPA prognosis remains poor despite advances in antifungal therapy. With voriconazole treatment, 12-week survival in neutropenic hematological malignancy patients is approximately 50–70%, though real-world outcomes vary considerably by underlying disease, depth of immunosuppression, and time to diagnosis. HSCT recipients with IPA have 12-week survival rates of 30–50%; cerebral aspergillosis reduces survival to less than 10% in most series. Azole resistance significantly worsens prognosis: patients with azole-resistant IPA have approximately doubled mortality compared to azole-susceptible disease. Predictors of poor outcome include cerebral dissemination, prolonged neutropenia unable to be reversed, renal failure, steroid doses equivalent to prednisolone >2 mg/kg/day, late diagnosis, and pan-azole-resistant A. fumigatus. Early CT diagnosis enabling antifungal initiation within the first few days of halo sign appearance has improved outcomes substantially compared to the pre-CT era.
9. Prevention
Prevention of IPA in high-risk patients combines environmental measures with pharmacological prophylaxis. Environmental control in inpatient settings for prolonged neutropenia and HSCT centers on HEPA filtration (removing particles >0.3 μm, effectively filtering fungal conidia) combined with positive-pressure laminar airflow rooms to prevent spore ingress. During hospital construction and renovation — high-risk events for aspergillosis outbreaks — infection control measures include sealing ward areas from dust, providing alternative routes for immunocompromised patients, and enhanced environmental surveillance cultures. Patient education about avoiding high-risk exposures (compost heaps, construction sites, soil disturbance) during the period of maximal immunosuppression is important for ambulatory management.
Antifungal prophylaxis is the standard of care in defined high-risk populations. Posaconazole (300 mg oral daily or 200 mg three times daily with food) is recommended for primary prophylaxis during AML induction chemotherapy and for GVHD treatment on corticosteroids: the pivotal randomized controlled trial (Ullmann 2007) demonstrated significant reduction in proven and probable fungal infections compared to fluconazole or itraconazole. Voriconazole is recommended as prophylaxis in lung transplant recipients. In HSCT recipients not receiving GVHD treatment, the optimal prophylaxis agent and duration remain debated. Micafungin and other echinocandins are used in centers with high azole-resistance prevalence. Aerosolized liposomal amphotericin B delivered by inhalation is under investigation as a lung-targeted prophylaxis. Reversal of immune compromise — shortening neutropenia through growth factor support (G-CSF), reducing corticosteroid doses as rapidly as clinically feasible, and addressing modifiable immunodeficiencies — is the most impactful preventive strategy. Galactomannan surveillance (twice-weekly serum GM in high-risk HSCT patients) enables preemptive antifungal therapy when GM turns positive before clinical symptoms develop, potentially improving outcomes compared to treating fully established IPA.
10. Recent Research
The most urgent research priority in aspergillosis is the global rise of azole-resistant Aspergillus fumigatus. The TR34/L98H mutation in the CYP51A gene — encoding the target enzyme of all triazole antifungals — confers pan-azole resistance and has been found in environmental isolates from agricultural soils exposed to demethylation inhibitor (DMI) fungicides across Europe, South Africa, Bangladesh, India, and China. Population genomic studies confirm environmental acquisition (not patient-to-patient transmission) as the dominant route of resistance emergence, raising concerns about the sustainability of triazole use in both medicine and agriculture sharing the same azole chemical scaffold. Surveillance networks in the Netherlands and UK report azole-resistant A. fumigatus in 10–30% of environmental samples in some regions; clinical isolates from IPA patients in these areas show azole resistance in 5–20% of cases, associated with significantly higher mortality.
Novel antifungal agents targeting resistant strains are in active development. Olorofim (formerly PC945 and F901318) is the first of a new class — the orotomides — that inhibits dihydroorotate dehydrogenase (DHODH) in the fungal pyrimidine biosynthesis pathway, a target not shared with any existing antifungal. Olorofim has demonstrated activity against azole-resistant and amphotericin B-resistant Aspergillus species in phase 2 trials and received FDA Breakthrough Therapy designation. Ibrexafungerp (a triterpenoid glucan synthase inhibitor), rezafungin (long-acting echinocandin), and novel tetrazoles are under clinical evaluation. Biomarker-guided preemptive strategies — initiating antifungals when galactomannan or PCR turns positive rather than waiting for clinical signs — are being refined in prospective trials in HSCT recipients, with results suggesting reduced antifungal exposure and equivalent outcomes to universal prophylaxis in moderate-risk populations. Single-center and retrospective studies of combination antifungal therapy (voriconazole plus anidulafungin) suggested a survival benefit in IPA, but prospective randomized data are awaited. Improved understanding of host genetic susceptibility — particularly IFNG, CLEC7A (Dectin-1), and TLR polymorphisms — is informing risk stratification models that could identify which patients truly require prophylaxis.
11. References
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