Invasive fungal infection in neutropenia

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Neutrophils are the principal effector cells against mould hyphae and important in Candida control. Cytotoxic therapy disrupts mucosa and suppresses inflammatory signs; corticosteroids impair macrophage and cellular function. As a result, fever may be the only early sign, local pain can precede visible inflammation, and infection may progress despite a normal chest radiograph or low CRP.

The fungal differential is shaped by time and exposure. Candida bloodstream and hepatosplenic disease follow mucosal or catheter entry. Aspergillus causes most invasive mould infection, but Mucorales, Fusarium, Scedosporium and endemic or rare fungi require different drugs. Prior prophylaxis changes both likelihood and susceptibility; voriconazole breakthrough should make Mucorales especially visible in the differential.

Centres use empirical or biomarker-driven pre-emptive strategies. Empirical therapy treats persistent high-risk fever despite antibacterials; pre-emptive therapy uses serial biomarkers and CT to target antifungals. Either strategy requires rapid diagnostic access, daily expert review and a local algorithm. Neutropenic fever that responds to antibacterials should not automatically accumulate antifungal drugs.

Key points

Neutropenic sepsis is the immediate emergency: take peripheral and line blood cultures if this does not delay treatment and give empirical antibacterial therapy at once.
NICE first-line intravenous antibacterial treatment is piperacillin with tazobactam unless patient-specific allergy, prior resistant colonisation or local microbiology indicates another regimen.
Invasive fungal risk rises with profound neutropenia below 0.5 × 10⁹/L lasting more than seven days, acute leukaemia, allogeneic transplantation, graft-versus-host disease, corticosteroids and prior mould colonisation.
Persistent or recurrent fever after four to seven days of broad antibacterial treatment in a high-risk patient should trigger fungal assessment; fever alone is not a species diagnosis.
First-line fungal assessment combines urgent CT chest, serum galactomannan, 1,3-beta-D-glucan and mould PCR according to local policy, plus targeted sinus, brain or abdominal imaging.
Obtain BAL, sterile-site fluid or tissue for microscopy, culture, histology and molecular identification before antifungal therapy when safe; treatment must not wait in a deteriorating patient.
Empirical options include liposomal amphotericin B 3 mg/kg intravenously daily or caspofungin 70 mg intravenously once then 50 mg daily, chosen from prophylaxis, syndrome and local pathway.
Posaconazole modified-release prophylaxis for selected high-risk AML or MDS induction is 300 mg twice on day one then 300 mg once daily, with interactions and exposure monitored.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Prolonged neutropenia

Profound neutrophil depletion lasting beyond seven days removes the principal cellular defence against mould hyphae and invasive Candida.

Barrier disruption

Chemotherapy mucositis, central catheters and gastrointestinal injury permit endogenous Candida and environmental fungi to access sterile tissue.

Additional immune defects

Systemic corticosteroids, graft-versus-host disease, T-cell depletion and transplant immunosuppression compound neutropenia and substantially broaden the fungal spectrum.

Antifungal selection pressure

Mould-active prophylaxis reduces susceptible disease but selects breakthrough resistant Aspergillus or organisms outside the agent's spectrum.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Failed hyphal killing
Absent neutrophil oxidative and extracellular killing allows inhaled or translocated fungi to germinate and invade tissue.
2
Vascular invasion
Mould hyphae penetrate blood vessels, causing thrombosis, haemorrhage, infarction, necrosis and rapid dissemination to distant organs.
3
Muted inflammation
Profound neutropenia suppresses pus, infiltrates and local signs, so fever or focal pain may precede radiologically obvious disease.
4
Recovery inflammation
Returning neutrophils intensify inflammation around fungal lesions, sometimes worsening symptoms and imaging despite effective antifungal activity.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Persistent febrile neutropeniaRed flag

Fever continues or recurs after four to seven days of broad antibacterial therapy while profound neutropenia is expected to last beyond seven days.

Angioinvasive pulmonary signsRed flag

Dry cough, pleuritic pain, haemoptysis, hypoxaemia or CT nodules may reflect vascular invasion despite minimal auscultatory findings.

Rhino-orbital diseaseRed flag

Unilateral facial pain, blocked nose, black mucosa, cranial neuropathy, proptosis or visual deficit suggests invasive sinus mould and possible Mucorales.

Hepatosplenic candidiasis

Fever, right-upper-quadrant discomfort and cholestatic liver tests may emerge during neutrophil recovery with multiple liver or splenic microabscesses.

Disseminated lesionsRed flag

Necrotic papules, focal neurological deficits, retinal findings, muscle pain or new organ dysfunction can reveal haematogenous fungal spread.

Red flags requiring action

Hypotension, rising lactate, confusion, oliguria, respiratory distress or rapidly progressive organ dysfunction requires immediate sepsis resuscitation and critical-care review.
Neutropenia at or below 0.5 × 10⁹/L with fever above 38°C or other clinically significant sepsis meets the NICE definition of neutropenic sepsis.
New pleuritic pain, haemoptysis, focal hypoxaemia or pulmonary nodules during prolonged neutropenia suggests angioinvasive mould disease.
Facial pain, nasal eschar, orbital swelling, ophthalmoplegia or visual change raises invasive fungal sinusitis and mandates urgent ENT, ophthalmic and surgical assessment.
A necrotic skin lesion, focal neurological sign, persistent abdominal pain or liver or spleen lesions may be the accessible clue to disseminated fungal disease.
Breakthrough infection while taking posaconazole or another mould-active prophylactic demands level and adherence review, susceptibility testing and usually treatment from another antifungal class.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Immediate sepsis culturesFirst step
Why
Identify bacterial or fungal bloodstream infection while preserving the no-delay emergency antibiotic standard.
Interpretation and limitations
Take peripheral cultures and paired cultures from every central-lumen type where feasible before therapy; never delay empirical antibacterials to complete a difficult draw.
02
First-line thin-section CT chestFirst line
Why
Detect early nodules, halo haemorrhage, infarcts, consolidation or cavitation missed by plain radiography.
Interpretation and limitations
Obtain urgently for persistent fever or focal respiratory features. Findings support probable mould disease and direct BAL or biopsy but are not organism specific.
03
Serum galactomannan
Why
Support invasive Aspergillus diagnosis and enable serial biomarker-led pathways in selected haematology populations.
Interpretation and limitations
Sensitivity falls during mould-active prophylaxis, while false positives occur. A trend must be integrated with CT, BAL and antifungal exposure.
04
Serum 1,3-beta-D-glucan
Why
Screen for a range of invasive fungi including Candida, Aspergillus and Pneumocystis.
Interpretation and limitations
It is not species specific and is usually negative in Mucorales; blood products, filters and some antibiotics can cause false positivity.
05
BAL fungal panel
Why
Sample the involved lung for microscopy, culture, Aspergillus galactomannan, PCR and alternative respiratory pathogens.
Interpretation and limitations
Target the CT lesion and send adequate volume before therapy when respiratory status permits; thrombocytopenia and hypoxaemia require a procedural risk plan.
06
Tissue histology, culture and PCR
Why
Demonstrate invasive hyphae in a sterile site and identify Aspergillus, Mucorales or another mould.
Interpretation and limitations
Direct fungal elements within tissue establish invasive disease, but morphology can misclassify species; pair pathology with culture and molecular sequencing.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Resistant bacterial sepsis

Persistent fever may reflect an uncovered Gram-negative, line infection, abscess or resistant colonising organism and needs renewed cultures and source review.

Viral infection

Respiratory viruses, CMV, HSV and VZV can cause fever or organ disease during cellular immune suppression and require targeted molecular testing.

Drug fever

Antibacterials, blood products and anticancer medicines can cause fever, but dangerous occult infection must be actively excluded first.

Malignancy-related fever

Active leukaemia, lymphoma, tumour necrosis and cytokine therapies produce fever that remains a diagnosis after systematic infection assessment.

Non-infectious lung injury

Pulmonary oedema, alveolar haemorrhage, treatment pneumonitis and engraftment syndrome can mimic diffuse fungal pneumonia on CT.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01FIRST HOURTreat neutropenic sepsisFirst stepA patient receiving anticancer treatment becomes unwell with suspected neutropenic sepsis.

1Perform ABCDE, lactate, FBC, renal and liver profiles, CRP and blood cultures, including central-line cultures where feasible, while summoning haematology and critical-care support.
2First lineAlternativeGive piperacillin-tazobactam immediately as NICE first-line beta-lactam monotherapy unless allergy, prior resistant carriage, infection site or local surveillance dictates an alternative.
3A common adult regimen is piperacillin-tazobactam 4.5 g intravenously every six to eight hours, adjusted for renal function and the locally approved neutropenic-sepsis protocol.
4Do not add an aminoglycoside or glycopeptide routinely; use additional coverage only for a defined clinical or microbiological indication.

02FUNGAL TRIGGEREscalate diagnostic intensityEscalationHigh-risk neutropenia has persistent or recurrent fever after four to seven days, or fungal focal signs appear at any time.

1Re-examine skin, mouth, line sites, sinuses, eyes, chest, abdomen and neurology and review every culture, drug, prophylactic dose and prior resistant isolate.
2Obtain urgent CT chest and site-directed sinus, brain or abdominal imaging; send serum galactomannan, beta-D-glucan and mould PCR under the centre pathway.
3Pursue BAL, biopsy or aspiration rapidly when safe, asking for histology, microscopy, fungal culture, PCR, species identification and susceptibility.
4Discuss empirical versus biomarker-led treatment the same day with haematology, infection, mycology and pharmacy rather than making fever duration the only decision.

03EMPIRICALStart broad fungal coverHigh-risk persistent fever or clinical deterioration makes occult fungal disease likely and diagnostic evidence is not yet available.

1Use liposomal amphotericin B 3 mg/kg intravenously every 24 hours or caspofungin 70 mg intravenously once then 50 mg every 24 hours according to the local empirical protocol.
2Prefer a different antifungal class when disease breaks through mould-active prophylaxis and obtain a prophylactic drug level, adherence history and urgent tissue.
3DefinitiveIf CT or tissue suggests invasive aspergillosis, use an Aspergillus-active definitive regimen; if Mucorales is plausible, use higher-dose liposomal amphotericin and arrange urgent surgical debridement.
4Reassess daily and stop or narrow empirical treatment when high-quality imaging, serial biomarkers, microbiology and clinical trajectory make fungal disease unlikely.

04TARGETConvert to organism-directed therapyImaging, antigen, culture, molecular testing or histology identifies a probable or proven fungal syndrome.

1AlternativeFor invasive aspergillosis, start or continue voriconazole or an appropriate alternative with therapeutic drug monitoring and susceptibility-directed adjustment.
2For candidemia, use an echinocandin, repeat blood cultures to clearance, remove the implicated line when feasible and investigate metastatic sites.
3For mucormycosis, use liposomal amphotericin B commonly 5 mg/kg intravenously daily, increase for CNS disease under specialist protocol and debride necrotic tissue urgently.
4Define duration from organism, anatomic resolution, source control and immune recovery; isolated fever resolution is not an adequate stopping rule.

05PROPHYLAXISPrevent infection in highest-risk periodsAML or MDS induction, allogeneic transplantation with graft-versus-host disease or another protocol-defined risk predicts prolonged profound immune suppression.

1Use posaconazole modified-release 300 mg orally twice on day one then 300 mg once daily when the haematology protocol identifies a mould-prophylaxis indication.
2Check azole interactions before anticancer, calcineurin-inhibitor or venetoclax prescribing and arrange therapeutic drug monitoring according to local mycology policy.
3Document start and stop dates against neutrophil and immune recovery; do not continue prophylaxis indefinitely without a current risk indication.
4If fever or CT lesions occur during prophylaxis, measure exposure, obtain urgent fungal diagnostics and assume the breakthrough organism may be resistant or outside the prophylactic spectrum.

Key medicines and prescribing safety5 treatments · regimens, roles and cautions

NICE-recommended initial beta-lactam monotherapy for suspected neutropenic sepsis unless patient-specific or local microbiological factors contraindicate it.

Piperacillin-tazobactam

A common adult neutropenic-sepsis regimen is 4.5 g intravenously every six to eight hours, started immediately and adjusted for renal function and local protocol.

Check immediate penicillin allergy, previous resistant Gram-negative carriage, renal function, sodium load and thrombocytopenia; culture collection must not delay the first dose.

Broad empirical yeast and mould cover, including activity against many Mucorales, while diagnosis is clarified.

Liposomal amphotericin B empirical

Give 3 mg/kg intravenously every 24 hours for empirical high-risk persistent febrile neutropenia under the local antifungal pathway.

Monitor creatinine, potassium, magnesium, FBC and infusion reactions; use 5 mg/kg or another dose only for a defined organism or site under specialist direction.

Evidence-supported alternative empirical antifungal for persistent febrile neutropenia, particularly when renal toxicity is a concern.

Caspofungin empirical

Give 70 mg intravenously once, then 50 mg intravenously every 24 hours; follow product guidance for weight above 80 kg and hepatic impairment.

It does not cover Mucorales and is not standard sole primary treatment of invasive aspergillosis; monitor liver function, interactions and diagnostic evolution.

First-choice mould-active prophylaxis for selected AML or MDS intensive induction and other defined high-risk haematology settings.

Posaconazole modified-release prophylaxis

Give 300 mg orally twice on day one, then 300 mg orally once daily from day two during the protocol-defined high-risk period.

Modified-release tablets and suspension are not dose interchangeable; monitor liver tests, QT, exposure and major interactions, particularly with venetoclax and calcineurin inhibitors.

Urgent first-line antifungal backbone for Mucorales alongside surgical debridement and reversal of immune or metabolic risk.

Liposomal amphotericin B for mucormycosis

Give 5 mg/kg intravenously every 24 hours for suspected or proven invasive mucormycosis, with higher CNS dosing only under a specialist protocol.

Do not delay for species confirmation when tissue necrosis progresses; monitor renal and electrolyte toxicity and arrange repeated surgical assessment.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Disseminated mould infection

Unchecked angioinvasion seeds brain, skin, kidneys and other organs, producing tissue infarction, haemorrhage and multiorgan failure.

Massive pulmonary haemorrhage

Vascular erosion around invasive pulmonary lesions can cause sudden life-threatening haemoptysis, particularly during inflammatory neutrophil recovery.

Rhino-orbital cerebral spread

Invasive sinus mould extends through orbit and skull base, threatening vision, brain and cavernous sinus without urgent debridement.

Hepatosplenic candidiasis

Persistent liver and splenic microabscesses become conspicuous during immune recovery and can require many months of antifungal treatment.

Antifungal toxicity

Renal injury, electrolyte loss, hepatic dysfunction, QT effects and drug interactions can interrupt lifesaving therapy or anticancer treatment.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Review physiology, lactate, fever curve, oral and skin examination, line sites, respiratory symptoms and focal pain at least daily; neutropenia can hide pus and peritonism.
Track neutrophil duration rather than one count, because risk depends on depth, expected recovery and corticosteroid or cellular immune impairment.
Repeat galactomannan or other biomarkers only within a validated serial pathway and interpret them against prophylaxis, transfusions, imaging and changing pre-test probability.
Monitor triazole levels and interactions, amphotericin renal and electrolyte toxicity and echinocandin liver tests; coordinate dose changes with specialist pharmacy.
Repeat CT at an interval driven by deterioration or treatment response, recognising that lesions can enlarge during early neutrophil recovery despite microbiological control.
Document organism, susceptibility, exposure, total duration, prophylaxis after treatment and instructions for immediate presentation during future neutropenic cycles.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Antibiotics remain first

Fungal risk never justifies delaying the immediate antibacterial dose in suspected neutropenic sepsis because early bacterial mortality is substantial.

Fever is a trigger

Persistent fever should activate imaging and mycology, but it does not distinguish Candida, Aspergillus, Mucorales, resistant bacteria or drug reaction.

Prophylaxis reshapes disease

A mould appearing during adequate azole exposure is enriched for resistant Aspergillus or intrinsically less susceptible organisms, making tissue and class switching important.

Recovery can enlarge lesions

Neutrophil return may increase inflammation and radiological lesion size before later improvement; interpret scans alongside physiology and fungal markers.

Skin offers diagnostic access

A necrotic papule can be safer to biopsy than a pulmonary nodule and may rapidly identify Fusarium, Aspergillus or another disseminated mould.

11Common pitfallsFrequent interpretation and management errors.

01
Do not delay empirical antibacterial therapy to complete cultures, CT or fungal biomarkers in suspected neutropenic sepsis.
02
Do not add vancomycin or an aminoglycoside routinely without a clinical, device, resistant-organism or local microbiological indication.
03
Do not rely on chest radiography or absence of cough to exclude invasive mould disease during profound neutropenia.
04
Do not diagnose invasive fungal infection from one isolated biomarker without considering false positivity, prophylaxis and imaging.
05
Do not continue the same prophylactic triazole as sole treatment for credible breakthrough invasive mould disease without level, susceptibility and class review.
06
Do not give voriconazole when mucormycosis is plausible; it lacks activity and can delay amphotericin plus debridement.