Diabetes mellitus (DM) is a metabolic disorder characterized by chronic hyperglycemia that may produce long-term com- plications like retinopathy, neuropathy, and nephropathy¹. Several immune alterations have been described in patients with diabetes, including progressive worsening of cellular immunity². Thus, patients with DM are more prone to fungal infections than healthy individuals. Cutaneous candidiasis is a common infection associated with DM³ that manifests as bright red plaques that can be erosive, dry, scaly, oozing, or macerated; pustules and collarette scales may also be present⁴. Clinically, cutaneous candidiasis lesions may show morpho- logies similar to those of other diseases, such as psoriasis, characterized by well-demarcated, thick, scaly, erythematous plaques, which could confuse clinicians. Here, we report a case of cutaneous candidiasis in the lower legs of a patient with uncontrolled DM.

A 67-year-old woman visited the hospital with complaints of painful, scaly plaques and crusts on both her lower legs, along with a one-year history of severe nail dystrophy (Fig. 1). Her past medical history was significant for DM, hypertension, and hyperlipidemia. The lesions first appeared as 5-6 ery- thematous papules on her left foot after receiving her first COVID-19 vaccination. After the second dose, she developed additional erythematous scaly papules and plaques on the left foot, and new annular erythematous lesions appeared on the right foot. She was diagnosed with an allergic reaction to the vaccine at a local clinic and was prescribed oral and topical steroids. However, after four months of treatment, the lesions became painful and began to ooze. Another local clinic diagnosed her with psoriasis and prescribed topical steroids; however, the lesions did not improve and she was referred to the dermatology department.

Figure 1. Demarcated erythematous scaly plaques and crusts are evident on the patient's legs and feet.

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On assessment, she had wide-spread painful, demarcated erythematous scaly plaques and crusts on both feet and lower legs and severely dystrophic toenails. No abnormal findings were observed during the system review. Blood tests showed elevated blood glucose (250 mg/dL; normal values: 70~99 mg/dL) and HbA1c levels (10.7%; normal range: 4.3~5.6%). The results of the complete blood count, liver function test, and renal function test results were all within normal limits. With the initial impression of plaque psoriasis and fungal infection, a KOH smear, fungal culture, and skin biopsy were performed. The KOH smear revealed numerous hyphae, confirming superficial fungal infection. Skin biopsy with H&E and D-PAS staining showed follicular plugging and crusts with numerous fungal spores and hyphae, which implied Candida infection rather than dermatophyte infection (Fig. 2). The fungus cultured from skin lesions isolated from Candida albicans. The final diagnosis was chronic cutaneous candidiasis, for which antifungal treatment with oral itra- conazole (200 mg daily) and topical amorolfine cream twice daily for 5 weeks. Unfortunately, the lesions did not improve substantially, and the treatment was changed to oral flu- conazole 150 mg weekly with topical sertaconazole cream for 5 weeks. After switching to fluconazole, her skin and nails started to significantly improve (Fig. 3).

Figure 2. Histopathological examination reveals follicular plugging with numerous fungal spores and hyphae (A: H&E stain 40×, B: D-PAS stain 400×).

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Figure 3. The bilateral lower extremity lesions appear improved after 5 months of antifungal treatment.

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People with DM are susceptible to various skin diseases, from infectious to autoimmune⁵. This is because they experi- ence prolonged hyperglycemia and insulin deficiency, which makes them more vulnerable to infections, neuropathy, suppression of cytokine production, defective phagocytosis, immune cell dysfunction, and a suboptimal immune response against bacteria⁶. Patients with DM also have a higher like- lihood of developing cutaneous fungal infections due to their high blood sugar levels, with a relatively high incidence of tinea pedis and onychomycosis ⁵.

Candida yeasts are common in the environment and can be found on human skin and in the oropharyngeal, respiratory, gastrointestinal, and genital areas⁹. These yeasts can cause various infections, from mild mucosal or skin issues to severe, life-threatening, and invasive infections⁷. Candida skin in- fections are quite common, affecting people of all ages and accounting for about 1% of all outpatient visits to dermato- logical clinics and 7% of all inpatient visits⁸. Some of the most common fungal pathogens that cause skin and nail infections include Candida albicans and Candida tropicalis¹¹. Typically, the infection begins with a pruritic rash that contains vesiculopustules, which then enlarge and often progress to maceration and erythema. The affected area has a scalloped border with a white rim of necrotic epidermis surrounding the erythematous macerated base, and satellite lesions are frequently observed¹¹. Candida folliculitis is mainly found in hair follicles and rarely becomes extensive¹¹. While all body regions may be involved, the most common areas affected are intertriginous areas, such as the groin folds, abdominal skin folds, inframammary folds, and interdigital spaces4.

Cutaneous candidiasis is a fungal infection that affects the skin. While it can be treated with antifungal medication, its clinical presentation can be similar to that of other skin conditions, leading to delayed diagnosis and treatment. Mis- diagnosis of cutaneous candidiasis occurred in a case of cutaneous candidiasis that mimicked acute generalized exan- thematous pustulosis (AGEP). A 67-year-old male with mul- tiple comorbidities presented with pruritic pustular eruptions and fever (38.2℃). Because he was previously treated with a 7-day course of antibiotics for bacteremia, the initial diagnosis was AGEP. However, a KOH examination and fungal culture revealed a cutaneous Candida infection, and the patient responded well to topical and oral antifungals. Zhang et al.¹⁰ reported in the case of an otherwise healthy 21-year-old male who presented with facial cutaneous candidiasis, which manifested as acne-like lesions, including papules, comedones, pustules, and cysts on both cheeks. He was initially diagnosed with acne; however, the lesions worsened despite treatment with oral minocycline. Because the fungal culture revealed C. albicans, topical and oral antifungals were prescribed, and the skin lesions improved. Patients with chronic mucocutaneous candidiasis may present with erythematous scaly plaques that resemble plaque psoriasis⁹.

Current treatments for cutaneous candidiasis typically in- volve topical and oral therapies with anti-inflammatory, anti- bacterial, and antifungal effects⁸. A systematic review of treat- ment strategies found that topical clotrimazole, nystatin, and miconazole were equally effective⁸. Fluconazole is currently the only evidence-based option for systemic treatment⁸.

Skin lesions caused by candidiasis can often resemble other skin diseases, making diagnosing difficult. If misdiagnosed and treated with steroids, it can further complicate the con- dition and delay proper treatment. Therefore, conducting a complete examination and taking a detailed medical history is crucial to ensure a correct and prompt diagnosis, especially in patients with multiple underlying health issues.