Title: Disseminated Magnusiomyces
Submitted by: Tristan Jones, MD, Christopher Doern, PhD, and Megan Morales, MD
Institution: Virginia Commonwealth University Health System
Email: Tristan.jones@vcuhealth.org
Date Submitted: 4/3/2026
Resubmitted: 6/4/2026
History: A 37-year-old man with past medical history of splenectomy and recurrent stage IV melanoma with metastases to the peritoneum, liver, and brain, on targeted chemotherapy, was admitted to the hospital with dyspnea, abdominal pain, tachycardia, and leukocytosis. He was initially maintained on antimicrobial prophylaxis with acyclovir and fluconazole and started empiric treatment with cefepime and metronidazole. While admitted he underwent tumor-infiltrating lymphocyte therapy, which involved immunoablation with fludarabine and cyclophosphamide. On post-transplant day (PTD) 0 he developed shock with multi-organ failure requiring intubation and renal replacement therapy. He was treated with broad-spectrum antibiotics and micafungin. He remained afebrile (maximum temperature 37.6°C) but shock persisted for >1 week, during which time he was treated with 20% dextrose-containing solution via central venous catheter for nutrition.
Physical Examination:
Ill-appearing young man, intubated and sedated. Abdominal distension, grimacing with abdominal palpation with no guarding, tympanitic, hypoactive bowel sounds. Bilateral pitting edema of lower extremities. Diffuse petechial rash on trunk and extremities.
Laboratory Examination:
Post-transplant day 0:
Total serum bilirubin 0.7 mg/dL
Serum alkaline phosphatase 37 U/L
White blood cells 400 x 106/L
Platelets 83 x 109/L
1,3-β-D-glucan 64 ng/L
Post-transplant day 10:
Total serum bilirubin 3.7 mg/dL
Serum alkaline phosphatase 69 U/L
White blood cells <100 x 106/L
Platelets 6 x 109/L
1,3-β-D-glucan 206 ng/L
Question 1: What are probable/possible diagnoses?
Possible etiologies for septic shock are extensive, however, the positive 1,3-beta-D-glucan raises concern for a fungal infection such as candidiasis.
Microbiology/Diagnostic Tests Performed:
Imaging:
PTD 1 CT angiogram abdomen and pelvis: known sequelae of metastatic melanoma. New small bilateral pleural effusions with small focal consolidation in right lower lobe.
PTD 15 CT chest, abdomen, pelvis: large bilateral pleural effusions with extensive collapse of both lungs, with patchy airspace disease in aerated portions of lung. Ongoing diffuse peritoneal and abdominal metastases.
Microbiology:
PTD 0 blood culture resulted negative at five days. PTD 1 respiratory culture from endotracheal aspirate grew moderate yeast that was not further identified. On PTD 10, blood culture collected on PTD 9 turned positive for yeast, not identifiable on PCR panel (bioMérieux). The organism grew as dry, flat, opaque, white colonies on blood and Sabouraud dextrose agar. It was identified as Magnusiomyces clavatus by MALDI-TOF with a match score of 1.86. Daily blood cultures continued to grow this organism through PTD 13. Susceptibility testing returned minimal inhibitory concentrations (MICs) as follows: amphotericin B 1.0 µg/mL, micafungin 4.0 µg/mL, fluconazole 8.0 µg/mL, isavuconazole 0.25 µg/mL, posaconazole 0.25 µg/mL, and voriconazole 0.06 µg/mL. Though standardized breakpoints are not established, based on Candida species, this would be considered susceptible to amphotericin and second-generation triazoles but resistant to micafungin and fluconazole, both of which the patient had received.
Final Diagnosis: Disseminated Magnusiomyces infection
Question 2: What treatment is recommended in the care of this patient?
Treatment: Micafungin was discontinued and treatment with liposomal amphotericin B (5mg/kg/day) and voriconazole (5mg/kg/dose BID) was initiated while awaiting antimicrobial susceptibility testing results. All central venous catheters were removed. A transthoracic echocardiogram was negative for valvular vegetations. Aggressive supportive care with mechanical ventilation, renal replacement therapy, vasopressors, blood product transfusions, and parenteral nutrition was continued.
Outcome: The patient had a fever on PTD 12. Neutrophil recovery started on PTD 14. He remained on liposomal amphotericin B and voriconazole in addition to broad spectrum antibiotics, however, his shock and multisystem organ dysfunction worsened. He was transitioned to comfort measures and died on PTD 21.
Discussion: (500 words)
Magnusiomyces, which has variously been known as Saprochaetes, Blastoschizomyces, Dipodascus, and Geotrichum, is an opportunistic pathogen most often isolated from patients with hematologic malignancies.1 M. clavatus is more commonly isolated in clinical specimens than the closely related M. capitatus. Magnusiomyces has been implicated in a variety of infectious syndromes similar to those caused by Candida, including mucocutaneous infections, bloodstream infections, and disseminated infections with microabscesses in various organs that resemble chronic disseminated or hepatosplenic candidiasis.2
This patient was diagnosed by blood culture, which is the most common method of diagnosis. Serum 1,3-β-D-glucan was positive in this case, and in one small series was reported to be positive in 65% of cases of invasive Magnusiomyces.3 Its diagnostic role in this scenario is not well established.4
This patient had several risk factors for invasive fungal disease, including multiple recent antibiotics, neutropenia, and presence of central venous catheters.4 Yeast was also isolated from the respiratory tract in this patient, but it was not identified further. This may have reflected a higher burden of colonization with yeast. Though not typically considered a pulmonary pathogen, Magnusiomyces has been reported as a cause of pneumonia.5 However, in this patient there was no clinical evidence of pneumonia.
Both clinically relevant Magnusiomyces species are considered intrinsically resistant to echinocandins and variably resistant to first-generation triazoles such as fluconazole.1,6 Though neither CLSI nor EUCAST have established antifungal breakpoints or epidemiologic cutoff values for Magnusiomyces species, case series report favorable in vitro susceptibility and clinical outcomes with second-generation triazoles such as voriconazole.1 No comparative trials exist to guide treatment. The global guideline for diagnosis and management of rare yeast infections recommends using antimicrobial susceptibility testing to guide care, and suggests a combination of amphotericin B and either flucytosine or voriconazole as recommended regimens based on clinical data.7 Various other regimens that include amphotericin B in combination therapy with echinocandins or the other second-generation triazoles, isavuconazole and posaconazole, have been reported with successful outcomes.1,4,7 In this case, liposomal amphotericin B and voriconazole were selected empirically based on review of prior literature. Though susceptibility testing suggested the isolate was susceptible to both these agents, the blood cultures remained positive for several days and the patient succumbed to the infection despite antifungal therapy.
Key References:
1. Noster J, Koeppel MB, Desnos-Olivier M, et al. Bloodstream Infections Caused by Magnusiomyces capitatus and Magnusiomyces clavatus: Epidemiological, Clinical, and Microbiological Features of Two Emerging Yeast Species. Antimicrob Agents Chemother. 2022;66(2):e0183421. doi:10.1128/AAC.01834-21
2. Bobb B, Jones T, Hatfield B, et al. Photo Quiz: Appendiceal agony and hepatic havoc: exploring infection in the immunocompromised. J Clin Microbiol. 2025;63(4):e00562-24. doi:10.1128/jcm.00562-24
3. Forster J, Koc Ö, Koeppel MB, et al. β-1,3-d-Glucan and Galactomannan as Biomarkers for the Detection of Invasive Geotrichum and Magnusiomyces Infections: a Retrospective Evaluation. J Clin Microbiol. 2022;60(1):e0160721. doi:10.1128/JCM.01607-21
4. Arendrup MC, Boekhout T, Akova M, et al. ESCMID and ECMM joint clinical guidelines for the diagnosis and management of rare invasive yeast infections. Clin Microbiol Infect Off Publ Eur Soc Clin Microbiol Infect Dis. 2014;20 Suppl 3:76-98. doi:10.1111/1469-0691.12360
5. Jiang Y, Chen Z, Lv H, Jiang L, Fan Z. A Case of Pulmonary Infection Due to Magnusiomyces capitatus in a Non-Immunocompromised Patient with Cerebral Palsy. Infect Drug Resist. 2024;17:4369-4373. doi:10.2147/IDR.S471082
6. Bosaeed M, Alshehri RA, Albarrak DA, Sharif T, Alghamdi M, Alsunidy AA. An unexpected opportunist: Magnusiomyces capitatus infection in an immunocompetent patient. Med Mycol Case Rep. 2024;45:100663. doi:10.1016/j.mmcr.2024.100663
7. Chen SCA, Perfect J, Colombo AL, et al. Global guideline for the diagnosis and management of rare yeast infections: an initiative of the ECMM in cooperation with ISHAM and ASM. Lancet Infect Dis. 2021;21(12):e375-e386. doi:10.1016/S1473-3099(21)00203-6