A man with erythema and ulcers on legs

A 59-year-old male farmer from southern China noticed a red spot on the skin of both lower limbs without any obvious cause half a month ago. The red spot on the right side gradually turned into a bruise, which then ulcerated [Figure 1a and b]. The patient sought consultation at a community hospital, where he underwent several rounds of debridement and anti-infection treatment. Despite these interventions, there was no significant improvement, and the wound continued to worsen, with swelling in the surrounding tissues. Then, the patient presented to our hospital for further treatment. He has a 4-year history of autoimmune hemolytic anemia and a 1-year history of hepatitis B. Currently, he is on long-term oral prednisone acetate tablets (40 mg/dL) and has a history of blood transfusions. The patient denies any other infectious diseases. The complete blood count analysis revealed the following: white blood cell count = 7.93 × 109/L, neutrophil % count = 94.00%, hypersensitive C-reactive protein = 8.30 mg/L, and biochemical analysis showed no abnormalities. Upon admission, wound secretions and tissues were collected. A portion of the samples was initially spread on Columbia blood agar plates, MacConkey plates, Chocolate plates, and Sabouraud plates (all sourced from Zhengzhou Antu Biological Bioengineering Co., Zhengzhou, China) and incubated at 35°C in 5% CO2 for pathogen culture. The remaining samples underwent processing with a 10% concentration of KOH for direct microscopic examination. Under the microscope, we identified a thin, single bundle of colorless fungal hypha [Figure 1c]. After 24 hours of incubation, we observed white fluffy stolon growth on both Columbia blood agar plates and Sabouraud plates [Figure 1d]. After staining the fungus with lactophenol cotton blue, we observed its morphological characteristics: round or ovoid sporangia, non-septate and branched hyphae, and observable rhizoids [Figure 1e]. The fungus was identified as Rhizopus stolonifer by using MALDI-TOF-MS and ITS sequencing. Figure 1e displays more obvious rhizoids, a characteristic of the Rhizopus genus. Initially, the surgeon suspected a simple skin infection and performed a pathogen culture instead of a skin biopsy. The patient was then diagnosed with cutaneous mucormycosis caused by Rhizopus stolonifer. Due to economic reasons, the patient declined antifungal medication. Nevertheless, the surgeon opted for multiple debridements with liquid antiseptic dressings on the right side, followed by a skin graft. The erythema on the left side subsided with the use of medical liquid dressing. Following the procedure, the patient's wound recovered well, and he was discharged from the hospital. Currently, the patient is under continued follow-up.Figure 1: Erythema on the patient's legs (a), the patient's erythema was ulcerated (b), Direct microscopic examination of the patient's wound tissue material (c) ×10, morphology of Rhizopus stolonifer cultured from patient's tissues on Sabourand plate (d), lactophenol cotton blue staining morphology of Rhizopus stolonifer and its rhizoid (marked by red arrow) (e) ×400.DISCUSSION Mucormycosis is a significant invasive mycosis presenting diagnostic and therapeutic challenges, coupled with a high morbidity and mortality rate. Formerly referred to as zygomycosis, the term "zygomycetes" has been eliminated from recent fungal taxonomy. Depending on the infection site, mucormycosis is classified into clinical types, including pulmonary mucormycosis, nasal-orbital-cerebral mucormycosis, cutaneous mucormycosis, renal mucormycosis, gastrointestinal mucormycosis, and mucormycosis.[1] Cutaneous mucormycosis is considered the milder form with a lower case fatality rate. Among the pathogenic fungi in the mucormycosis order, Rhizopus is the most common.[1,2] In China, cases of cutaneous mucormycosis infected with irregular Rhizopus are relatively more prevalent.[3] Infections caused by Rhizopus stolonifer are currently rare in China, resulting in low prevalence. The patient had no history of traveling to areas where Rhizopus stolonifer is endemic. Rhizopus stolonifer has been predominantly found on the feet and exhibits a significantly higher presence in males than females, possibly related to foot hygiene practices in both sexes, as reported by Oyeka and Ugwu.[4] The patient's poor hygiene practices, coupled with the fact that he had been taking hormone medication for a long time, were what caused him to come into contact with Rhizopus stolonifer and thus become infected. Mucormycosis typically occurs in patients with serious underlying conditions such as diabetes, AIDS, and those taking hormone drugs for an extended period.[5] The patient in this case has been on hormone drugs for an extended time due to having both hepatitis B and hemolytic anemia, which are high-risk factors for cutaneous mucormycosis. Common manifestations of cutaneous mucormycosis include erythema, swelling, pustules, and necrosis.[1] In this instance, erythema appeared initially and eventually progressed to necrosis. Early detection and treatment are crucial. If the patient's skin lesions present as blisters or ulcers, efforts should be made to collect ulcerated tissue or crusts for fungal examination and culture to identify the pathogen. Performing fluorescent staining on necrotic tissue can serve as diagnostic evidence for mucormycosis when mucormycoid hyphae are discovered.[6] Treatment of mucormycosis should include early surgical intervention where permitted, involving local debridement and removal of infected tissue or organs. Antifungal drugs, with amphotericin B as the drug of choice, should be used when necessary. If single-drug treatment is not effective, a combination of drugs can be taken, and the combination of amphotericin B with either esaconazole or posaconazole can be chosen. Minimizing or discontinuing glucocorticoid or immunosuppressive drugs is also crucial.[1] For the prevention of mucormycosis, actively controlling the underlying diseases of susceptible people is essential. Patients with high-risk factors should avoid contact with items contaminated by mucormycosis, improve living environments by minimizing humidity and ensuring proper ventilation, and implement anti-mold measures. Patients who have suffered from mucormycosis, after complete or partial remission, can be given previously effective drugs when undergoing chemotherapy or hematopoietic stem cell transplantation again. Author contributions Yuhang Jiang wrote the manuscript, Weichao Qin collected the clinical data, and Yan Zeng reviewed the manuscript. Ethics statement The study was approved and complied with the requirements of the Ethics Committee at the Chongqing University Jiangjin Hospital, Chongqing. The patient provided written consent for the publication of this study. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.