Cladosporium species novum Invasive Pulmonary Infection in a Patient with Post-COVID-19 Syndrome and AIDS

<b>Background and Clinical Significance:</b> Since the prevalence of fungal lung infections is increasing, certain agents, such as <i>Cladosporium</i> spp., have emerged as unexpected causes. <i>Cladosporium</i> spp. fungi are ubiquitous in environments such as soil, fruits, and wine corks; they are a part of the normal human skin flora; and they are known respiratory allergens. <b>Case Presentation</b>: A patient with a history of post-COVID-19 syndrome and AIDS presented with lung pathology indicative of an invasive fungal infection. The initial histopathological examination revealed numerous yeast-like cells with narrow-based budding, which led to a mistaken diagnosis of cryptococcosis. However, further detailed examination revealed sparse hyphae in the lung tissue, suggesting a more complex fungal infection. Molecular analyses and sequence BLAST alignment were performed, ultimately identifying the infectious agent as "<i>Cladosporium species novum</i>", a rare cause of invasive pulmonary cladosporiasis. <b>Conclusions</b>: Invasive pulmonary cladosporiasis is a rare condition, and the morphological features of the fungus alone were insufficient to establish a correct diagnosis. A comprehensive pathohistological and molecular approach with bioinformatics tools is essential for the correct identification of rare and potentially life-threatening fungal pathogens in immunocompromised patients.