Case 1 was in a 46-year-old man in North Dakota, USA, who immigrated from Liberia in 2012. When he sought care in 2025, he had a 2-year history of localized pain, discomfort, and restricted movement over his right olecranon bursa. He reported no injury to the area, fever, night sweats, weight loss, or respiratory symptoms. His medical history was unremarkable, and he was taking no prescription medications. Magnetic resonance imaging demonstrated olecranon bursitis. After orthopedic evaluation, surgical excision of the bursa was conducted. Postoperative recovery was uncomplicated; sensation, motor strength, and range of motion were fully preserved.

Figure 1

Figure 1. Images of stained tissue specimen from olecranon bursa of case-patient 1 in study of chronic elbow nodules caused by Fomitiporellafungus in immunocompetent patients, United States. A) Hematoxylin and...

Histopathologic examination of the removed tissue revealed multiple large expansile granulomas bordered by epithelioid histiocytes. Gram and acid-fast stains were negative; alcian blue/periodic acid–Schiff staining showed focal dermal mucin and abundant fungal hyphae, and Grocott methenamine-silver stain highlighted numerous hyphae within granulomatous areas (Figure 1). Culture was not ordered. A formalin-fixed, paraffin-embedded (FFPE) tissue block was submitted to the University of Washington (UW) Molecular Microbiology Laboratory (Seattle, WA, USA) for molecular diagnosis.

Broad-range fungal PCR (10) targeting the 28S rRNA gene yielded a 610-bp sequence (GenBank accession no. PX488794) with 98.2% identity to Fomitiporella austroasiana (accession no. MG657323) and 98.03% identity to 2 F. austroasiana type strain sequences (accession nos. MG657320 and NG_060440). We corroborated the result by comparing a 316-bp internal transcribed spacer (ITS1) sequence (accession no. PX596867) to the same strains, which showed 98.2% identity to F. austroasiana (accession no. MG657323) and 90.77% identity to 2 type strain sequences (GenBank accession nos. MG657328 and NR_158435), establishing a molecular diagnosis of Fomitiporella species related to F. austroasiana. The patient received no antifungal therapy and remained well without recurrence.

Figure 2

Figure 2. Images of stained tissue specimen from olecranon bursa of case-patient 2 in study of chronic elbow nodules caused by Fomitiporellafungus in immunocompetent patients, United States. A) Hematoxylin and...

Case 2 was in a 43-year-old man in Washington who immigrated from Mexico in 2021. He sought care in 2025 for a painful, slowly enlarging nodule over his left olecranon bursa that had persisted for >5 years. He had no systemic symptoms or history of immunodeficiency. Surgical excision of the bursa was performed, and a specimen was submitted for histopathology. Immunohistochemical staining showed no infiltrative cytokeratin AE1/AE3 or CD34-positive cells. Although acid-fast staining results were negative, GMS stain revealed scattered fungal hyphae along the periphery of palisading granulomas (Figure 2). Histopathologic features were consistent with subcutaneous fungal infection. An FFPE tissue block was sent to the UW Molecular Microbiology Laboratory for broad-range fungal PCR.

A 608-bp 28S rRNA gene sequence from the specimen (GenBank accession no. PX488793) displayed 98.8% identity to F. micropora (accession no. MG806099). Results of 327-bp ITS sequencing of the reference strain (accession no. PX596866) provided orthologous support, showing 91.25% identity to F. micropora (accession no. KX181296). We established the molecular diagnosis of Fomitiporella species related to F. micropora on the basis of those results. The patient received no antifungal therapy and remained well without recurrence.

The 2 cases presented here implicate Fomitiporella spp. as human pathogens. In both cases, the DNA sequences identified exhibited sufficient sequence diversity from previously classified Fomitiporella spp. that they likely represent previously undescribed species in the genus. Case 1 involved a F. austroasiana–like species; case 2 involved a F. micropora lineage. Human infections attributed to Fomitiporella spp. are rarely reported in the literature; an infection involving a F. micropora lineage was previously identified by the UW Molecular Microbiology Laboratory in an immunocompromised patient in New York in 2025 (11). The cases we report demonstrate that Fomitiporella can cause disease in otherwise healthy hosts.

Clinicians initially considered chronic aseptic olecranon bursitis in both cases; histopathologic examination unexpectedly revealed fungal hyphae, prompting consultation with the infectious diseases service. Each of the 3 reported Fomitiporella infections have manifested as long-standing, localized cutaneous or subcutaneous lesions: 1 on the lower extremity (11) and 2, the cases we describe, involving the olecranon. That pattern suggests superficial soft tissue as a favored niche, possibly after environmental inoculation via unnoticed trauma or occupational exposure; for 1 patient, documentation indicated long-term employment in equipment assembly. In other implantation mycoses, patients often do not recall a specific traumatic event. Of note, all 3 reported infections have occurred in persons who immigrated from tropical or subtropical regions (Liberia, Mexico, and Trinidad), where wood-decaying Fomitiporella spp. are endemic (12), suggesting that patients acquired the infection before immigration. However, the apparent geographic distribution might partly reflect where environmental sampling for those fungi has been conducted.

Both of the case-patients we report were treated with surgical excision and no antifungal therapy. Although long-term follow-up data were not available, the clinical course in those cases and the previously reported case (11) suggested that surgical excision might be sufficient for localized Fomitiporella infection and with antifungal therapies reserved for incomplete excision, immunosuppressed patients, or evidence of dissemination. In cases where antifungal treatment is warranted, the limited evidence suggests that infections caused by filamentous basidiomycetes usually respond well to azoles other than fluconazole (7,13).

Filamentous basidiomycetes are rarely implicated in human infection and are often misidentified or overlooked. Awareness of Fomitiporella is important for pathologists who encounter fungal hyphae in granulomatous lesions without a definitive culture result. Molecular identification should be considered when cultures are sterile or yield nonsporulating hyaline molds. Reporting additional Fomitiporella cases will improve understanding of epidemiology, disease spectrum, and treatment strategies.

Fomitiporella spp. infection, although exceedingly rare, can cause chronic localized lesions in both immunocompetent and immunocompromised hosts. Complete surgical excision offers excellent outcomes without antifungal therapy in most patients. Broad-range fungal PCR can identify molds and yeasts and some nonfungal eukaryotic pathogens such as oomycetes, amoebae, and parasites (14,15); therefore, it is a valuable tool for diagnosing unusual or unexpected infections, even in cases in which material is not available for microbial culture. Clinical and laboratory awareness of the pathogenic potential of Fomitiporella spp. will contribute to increased recognition and prevent misdiagnosis of such potentially emerging pathogens.