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Rasamsonia species are thermophilic fungi that primarily cause infection in immunocompromised patients. R.argillacea species complex is frequently misidentified as a pathogen due to its morphological similarity to the genera Penicillium and Paecilomyces and its incidence remains undetermined. This situation further complicates the process of timely diagnosis and treatment. Rasamsonia species can be identified using internal transcribed spacer (ITS) sequence analysis, which is considered the primary fungal barcode. Accurate species identification is imperative for the administration of appropriate antifungal treatment. In this report, a case of acute myeloid leukaemia (AML) with R.argillacea growth was presented. A 69-year-old female patient diagnosed with AML who was undergoing chemotherapy was admitted to the hospital due to febrile neutropenia. Despite the administration of appropriate antibiotic therapy, the patient's fever did not respond and her respiratory distress worsened. A subsequent chest computerized tomography scan revealed the presence of bilateral nodular lesions and halo findings in some nodules. The empirical liposomal amphotericin B was initiated at a dosage of 3 mg/kg/day. Following a 17-day course of empirical amphotericin B therapy, the patient exhibited an escalation in respiratory distress and an increase in her blood galactomannan (GM) level (Platelia™ Aspergillus Ag; Bio-Rad, France). Consequently, intravenous (IV) voriconazole was administered at a loading dose of 2x6 mg/kg followed by a maintenance dose of 2x4 mg/kg. Notwithstanding the administration of voriconazole therapy, the patient's blood GM levels persisted at elevated levels on three separate occasions. Consequently, a bronchoalveolar lavage (BAL) sample was obtained for further analysis. However, no growth was detected in the bronchoalveolar lavage (BAL) culture. The BAL GM level was found to be elevated (optic indices: 4.38). The patient developed increasing respiratory distress and confusion and was intubated. A deep tracheal aspirate (DTA) sample was collected. The patient died shortly thereafter. Velvety, beige-colored colonies were observed in the culture media to which the DTA sample inoculated. Microscopic examination of the culture using a lactophenol cotton blue stain revealed cylindrical conidia, rough-walled conidiophores and long, pointed phialides. The isolate was identified as R.argillacea using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (Bruker, Bremen, Germany). This isolate could not be identified based on colony morphology and microscopic appearance; however, it was identified as R. argillacea using the ribosomal DNA ITS region. Its antifungal susceptibility was then assessed using the microdilution method according to the Clinical and Laboratory Standards Institute M38-A2 guidelines. The minimum inhibitory concentrations (MICs) for the antifungal drugs were as follows: fluconazole >64 μg/mL, itraconazole 0.5 μg/mL, voriconazole >16 μg/mL, posaconazole 0.5 μg/ mL, anidulafungin ≤0.015 μg/mL, micafungin 0.03 μg/mL and amphotericin B 1 μg/mL. In this case, the patient died without the causative agent being identified. Although it cannot be definitively stated that R. argillacea was the cause of the patient's mortality due to the lack of an autopsy, this case was presented because it is the first suspected case of R. argillacea isolated and confirmed by molecular methods in Türkiye and to highlight the importance of not neglecting Rasamsonia species which are rare mold fungi.