USMLE Guide: Candidiasis

Introduction

Candidiasis is a common fungal infection caused by the overgrowth of Candida species, most commonly Candida albicans. This infection can affect various parts of the body, including the skin, mucous membranes, and internal organs. It is important for medical students preparing for the USMLE to have a comprehensive understanding of candidiasis, including its clinical presentation, risk factors, diagnostic approaches, and treatment options.

Clinical Presentation

The clinical presentation of candidiasis depends on the affected site. It can manifest as:

• Oral Candidiasis (Thrush): Presents as white, curd-like patches on the oral mucosa, tongue, and/or buccal surfaces.
• Esophageal Candidiasis: Characterized by odynophagia (painful swallowing) and retrosternal discomfort.
• Vulvovaginal Candidiasis: Presents with vaginal itching, thick white discharge, and erythema.
• Cutaneous Candidiasis: Manifests as pruritic (itchy), erythematous (red), and sometimes satellite lesions in warm, moist areas of the skin.
• Invasive Candidiasis: Can cause systemic symptoms such as fever, chills, and hypotension. Organ-specific symptoms may also be present depending on the affected site (e.g., endophthalmitis, endocarditis, meningitis).

Risk Factors

Several risk factors contribute to the development of candidiasis, including:

• Immunosuppression: HIV/AIDS, chemotherapy, organ transplantation, and corticosteroid use.
• Diabetes Mellitus: Poor glycemic control predisposes individuals to candidiasis, especially in the oral and genital regions.
• Broad-spectrum Antibiotics: Disrupt the normal microbial flora, allowing Candida overgrowth.
• Pregnancy: Hormonal changes and altered vaginal pH increase the risk of vulvovaginal candidiasis.
• Obesity: Skin folds provide a favorable environment for candidal growth.
• Indwelling Catheters: Enable Candida colonization and subsequent infection.

Diagnostic Approaches

To diagnose candidiasis, various methods can be employed:

• Clinical Examination: Based on characteristic findings, such as white patches in oral thrush or genital itching in vulvovaginal candidiasis.
• Microscopic Examination: Microscopic examination of skin scrapings or vaginal swabs can reveal pseudohyphae and yeast cells.
• Culture: Candida colonies can be grown on Sabouraud agar.
• Serologic Testing: blood cultures can be performed for suspected invasive candidiasis.

Treatment Options

The treatment of candidiasis depends on the site and severity of infection:

• Oral Candidiasis: Topical antifungal agents such as nystatin or miconazole oral gel are the first-line treatment.
• Esophageal Candidiasis: Oral fluconazole is the preferred treatment, while severe cases may require intravenous antifungal therapy (e.g., amphotericin B).
• Vulvovaginal Candidiasis: Topical azole antifungals (e.g., clotrimazole, miconazole) or oral fluconazole are commonly prescribed.
• Cutaneous Candidiasis: Topical antifungal creams (e.g., clotrimazole, ketoconazole) are the mainstay of treatment.
• Invasive Candidiasis: Antifungal therapy with fluconazole or echinocandins is the treatment of choice, and the duration may vary depending on the clinical response.

Conclusion

Candidiasis is a common fungal infection caused by Candida species. Medical students preparing for the USMLE should be familiar with the clinical presentation, risk factors, diagnostic approaches, and treatment options for this condition. By understanding the key aspects of candidiasis, aspiring physicians can provide appropriate care to patients presenting with this infection.