To the Editor: Fungal infections in children awaiting hematopoietic stem cell transplantation (HSCT) pose significant therapeutic challenges.1, 2 Single infections involving uncommon yeasts or molds are infrequent,3, 4 and coinfections are exceedingly rare and poorly documented.5 We present a case of a child who developed a rare fungal coinfection before HSCT. The case highlights challenges in selecting antimicrobial agents, managing end-organ disease, and optimizing transplantation timing and therapy duration. An 11-year-old male was diagnosed with acute lymphoblastic leukemia in July 2022. After abandoning treatment, he presented to our institution in March 2023 with extensive bone marrow leukemic infiltration and was prescribed the UK-ALL R3 rescue protocol. On day 14 of profound neutropenia, he developed septic shock with multiple blood cultures positive for Trichosporon asahii (Supplementary Figure S1) and tender skin lesions (Figure 1). A skin biopsy culture confirmed Fusarium spp (antifungal susceptibilities not performed) (Supplementary Figure S2), and a panfungal PCR assay (CIB, Medellin, Colombia) only detected Fusarium spp. A PET scan revealed disseminated disease (Figure 2A), and ophthalmological examination identified bilateral retinocoroidal infiltrates. Liposomal amphotericin B (7.5 mg/kg/day) was combined with intravenous voriconazole (9 mg/kg every 12 hours) and four weekly intravitreal injections of voriconazole (0.05 mL per eye). Myelosuppressive chemotherapy was discontinued, and he underwent two cycles of blinatumomab to maintain temporary remission of leukemia. He remained febrile for 17 weeks but in adequate clinical condition and with negative fungal cultures and inflammatory markers. Despite persistent fevers, antibacterial therapy was withheld except for one episode during which empiric vancomycin and meropenem were urgently administered due to clinical deterioration. An ESBL+ Escherichia coli was detected in two blood cultures. On July 29, 2023, 14 weeks after the initial episode of mycotic sepsis, when his overall clinical condition, cultures, and laboratory biomarkers suggested infections were under control, the patient underwent a peripheral blood HSCT from his HLA 10/10 matched brother. Eleven months posttransplant, the patient remains leukemia- and mycosis-free. The patient received voriconazole for 9 months (mean therapeutic level: 2.5 µg/mL), and liposomal amphotericin B for 15 weeks. Antifungal therapy was discontinued 6 months post-HSCT after a repeat PET-CT scan (Figure 2B) confirmed the resolution of infectious lesions without metabolic changes suggestive of active infections. This was accompanied by normalized clinical and laboratory parameters and presumed immune reconstitution indicated by normal hematologic indices, absence of opportunistic infections, and absence of graft-versus-host disease or immunosuppressive medications. During the ophthalmological follow-up, his vision was counting fingers. Both retinas had zones of vitreoretinal traction without inflammatory infiltrates. Six months after cessation of antifungal therapy, he remains asymptomatic with no signs of leukemic or fungal relapse. Several aspects of this case merit attention. The limited information on this coinfection made selecting effective antifungal treatment challenging, especially without established breakpoints for rare yeasts and molds. We opted for high-dose liposomal amphotericin B combined with intravenous voriconazole based on guideline recommendations6, 7 and administered intravitreal voriconazole as previously described for Fusarium endophthalmitis.8 The optimal timing for initiating myeloablative conditioning for HSCT in patients with invasive fungal infections (IFI) is unclear. At a minimum, negative blood cultures, improvement in follow-up imaging, and reduction in inflammatory and fungal biomarkers, alongside clinical improvement, should be evident. This generally occurs after at least four weeks of appropriate antifungal therapy.9 Despite improved clinical and laboratory parameters, persistent fever can occur in deep-seated fungal infections, possibly due to immune reconstitution syndrome.10 In such cases, antibacterial therapy is not indicated. Healthcare team members must thoroughly understand their patients' clinical profiles to recognize subtle changes that may require urgent antibacterial treatment. All patients with bloodstream fungal infections should undergo a comprehensive evaluation to detect end-organ disease. PET-CT uses metabolic indices to quantify disease burden and to evaluate treatment efficacy.11 In our patient, antifungal therapy was discontinued when fungal lesions had resolved on PET-CT, clinical symptoms suggestive of IFI or graft-versus-host disease were absent, and absolute neutrophil and lymphocyte counts were greater than 1000 cells/mm3.12 However, considering the high risk of IFI relapse,13, 14 a careful follow-up after discontinuing antifungal therapy is mandatory. In this patient, there was simultaneous detection of Trichosporon asahii in blood cultures and Fusarium spp skin infection, likely due to hematogenous dissemination. This coinfection case highlights the importance of pursuing tissue diagnosis from skin lesions or deep-seated lesions in immunocompromised hosts, even when the etiology has been documented through repeated blood cultures. Patients in leukemic remission for whom HSCT is indicated but delayed due to infectious complications are at high risk of disease recurrence. Blinatumomab induces apoptosis in B cells without causing profound neutropenia.15 For patients with CD19+ B-cell acute lymphoblastic leukemia who develop severe infections requiring HSCT delay, blinatumomab can provide time to control the infection and prevent leukemia recurrence. As advances in chemotherapy and supportive care allow an increasing number of patients to reach the transplant period, better antifungal drugs and IFI-diagnostic capabilities will result in a growing number of HSCT patients with a recent invasive fungal disease. This case report offers significant insights into the management of an immunocompromised patient with IFI coinfection and allows discussion of some of the most critical aspects of the difficult peri-HSCT management of these patients. The authors declare no conflicts of interest. 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