Purpureocillium lilacinum, formerly Paecilomyces lilacinus, is a saprophytic fungus commonly found in soil and decaying plants¹. Although it is rarely pathogenic to humans, there have been a recent increases in reported cases of P. lilacinum infections¹. This describes a case of deep cutaneous mycosis caused by P. lilacinum in a farmer. The intent of this work is to raise awareness about such infections, especially among immunocompetent patients, and aid in selecting appropriate antifungal agents.

An 89-year-old woman, who worked as a farmer in a rural area, presented with a 3-month history of an erythema- tous patch and crusted nodule on her right forearm (Fig. 1) that developed after she was injured by a bamboo thorn. Initial treatment with steroids for allergic contact dermatitis worsened her symptoms. A 10% potassium hydroxide smear of a cutaneous scraping was negative. A right lower arm biopsy revealed diffuse inflammatory cell infiltration, gran- ulomatous lesions, and fungus-like organisms with H&E staining (Fig. 2-A). PAS staining was positive (Fig. 2-B), while AFB staining was negative. Gram staining, bacterial culture, and AFB culture all returned negative results.

Figure 1. The skin lesion consisted of erythematous patch with surface nodularity and yellowish crust on right forearm.

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Figure 2. (A) Granulomatous changes (right arrow) and fungus-like organisms (left arrow) were seen in the dermis (H&E, ×400). (B) Fungal hyphae were found among the inflam- matory cells upon periodic acid-Schiff staining (×400). (C) Light velvet pink and white colonies grew after a week of incubation on Sabouraud's media. (D) The reverse was dark brown. (E) Internal transcribed spacer (ITS) sequence of the rRNA gene was used to identify Purpureocillium lilacinum.

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Fungal culture on Sabouraud's medium for 1 week showed light velvet pink and white colonies (Fig. 2-C), with the reverse side brown and darker at the center (Fig. 2-D). The Department of Laboratory Medicine confirmed these find- ings. Fungal PCR testing using the MALDI-TOF MS method identified the organism as P. lilacinum (Fig. 2-E), ultimately diagnosing deep cutaneous mycosis caused by P. lilacinum. Oral itraconazole (200 mg/day for two weeks) was prescribed.

Subsequently, the patient was lost to follow-up but later admitted to the cardiology department due to NSTEMI. While her skin lesion showed significant improvement, continued antifungal treatment was necessary. Itraconazole, contra- indicated with statins and potentially leading to heart failure in some cases, necessitated MIC tests for alternative drugs. Voriconazole had the lowest MIC score (Table 1). However, as azole antifungals are contraindicated with statins, echino- candins like caspofungin or micafungin were considered suitable alternatives, pending P. lilacinum detection; however, the patient was lost to follow-up.

P. lilacinum, a saprophytic fungus typically found in soil and decaying plants, is rarely pathogenic to humans. However, there has been a recent uptick in P. lilacinum infections, predominantly affecting the skin and eyes. Skin infections manifest as patches, plaques, vesicles, pustules, nodules, and crusts, often accompanied by pain, pruritus, and tenderness. These lesions frequently occur in exposed areas like the face, arms, and legs, typically linked to trauma.

Immunosuppressive conditions such as diabetes mellitus, transplantation, malignancy, and the use of immunosuppressive drugs are known risk factors for P. lilacinum infection. However, soil exposure, trauma, and an agricultural lifestyle can also be risk factors in immunocompetent hosts. Several cases among farmers have been reported in Korea^2,3.

Diagnosis of P. lilacinum considers the patient's history, symptoms, clinical features, and occupational background. Diagnosis is primarily confirmed through culture results and microscopic findings. When cultured on Sabouraud's dextrose agar, P. lilacinum colonies grow rapidly within 14 days. While they initially appear white, over time they turn to shades of white to vinaceous or velvet pink with shallow wrinkles. The reverse side may display a vinaceous color but can also be brown or dark brown. To rule out contamination, recom- mendations are to culture samples in at least two media and comparing the results. Common biopsy findings include inflammation, granuloma, and fungal organisms. Molecular approaches, such as small subunit ribosomal sequence analysis, aid in more accurate fungal identification.

There is no consensus on empirical antifungal drugs for P. lilacinum infection; therefore, conducting a MIC test is advisable. Treatments include surgical debridement and systemic antifungal agents. However, the lack of established treatment guidelines underscores the importance of relevant case reports (Table 2). In many cases, Amphotericin B, flucytosine, and fluconazole have shown high resistance⁴. Itraconazole, despite its varied MIC values is commonly administered, and most patients improve clinically. Azole antifungals were initially used in this case, leading to clinical improvement; however, her recovery was incomplete. Due to drug–drug interactions with statins, echinocandin therapy, such as caspofungin or micafungin, was considered. Despite being lost to follow-up; this case provides valuable insights for future treatment of P. lilacinum infections in patients with cardiovascular condi- tions. Posaconazole and voriconazole—showing the lowest MIC in many cases—should be considered for cases unrespon- sive to itraconazole. There have been successful reports of treating P. lilacinum skin infections with voriconazole^9,13.

Korean cases of P. lilacinum included lesions concentrated on exposed areas such as the face and arms, and there have been many infections in farmers^2,5. Similar to this case, there were many cases of treatment starting with itraconazole and being ultimately curative¹⁴. However, there was a case in which voriconazole resulted in clinical improvement after none had been seen over 14 weeks of itraconazole administration⁹. In conclusion, the initial treatment should be itraconazole in patients with confirmed P. lilacinum infections. If the treatment response is unclear, it is necessary to consider switching the drug according to the MIC test. Therefore, if the MIC test is impossible, take Posaconazole or Voriconazole empirically.