Genital candidiasis includes vulvovaginal candidiasis in women and candidal balanoposthitis in men. Candida is a conditional pathogenic fungus, and generally healthy women can carry Candida without clinical symptoms, with pregnant women being more likely to be carriers. Certain factors, such as reduced body resistance, can lead to the overgrowth of Candida and cause disease. It can be transmitted to sexual partners through intercourse, but can also be indirectly transmitted through objects. The main pathogenic fungus is Candida albicans.

bubble_chart Epidemiology

Vaginal candidiasis is one of the most common diseases in women's vaginal infections. Due to the widespread use of broad-spectrum antibiotics and corticosteroids, the incidence of this disease is continuously increasing, becoming the most significant disease cause of increased leucorrhea.

Vaginal candidiasis is commonly seen in women from adolescence to pre-menopause, while the incidence is relatively lower in young girls who have not yet menstruated and postmenopausal women. In asymptomatic healthy women of childbearing age, the detection rate of Candida in the vagina is about 20%. Factors such as pregnancy, contraceptive use, and diabetes can increase the carrier rate.

The detection rate of Candida on the male penis is closely related to whether the foreskin is overly long. Men with phimosis who have not undergone circumcision have a higher detection rate of penile Candida than those who have been circumcised. Among the sexual partners of women with vaginal candidiasis, the genital Candida infection rate is as high as 70%. Women with vaginal candidiasis have spouses with a Candida detection rate on the penis more than four times that of men in the control group. Among women who have sexual contact with Candida-positive men, the Candida infection rate is 80%, compared to 32% in women who have sexual contact with Candida-negative men. This shows that genital candidiasis is closely related to sexual contact, and vaginal Candida and Candida balanitis can be mutually transmitted through sexual contact.

The majority of pathogenic fungi are Candida albicans, with some being other Candida species and Torulopsis. Currently, cases caused by Torulopsis infection are increasing and should be taken seriously.

Candida is widely distributed in nature and is one of the normal flora of the human body, primarily colonizing the oral cavity, skin, vagina, and internal organs. The carrier rate of Candida albicans in the normal population can be as high as 40%; 85–90% of Candida isolated from the vaginal mucosa is Candida albicans, which has the strongest pathogenic potential.

Candida belongs to the Fungi kingdom, Deuteromycotina subphylum—Blastomycetes class—Cryptococcales order—Cryptococcaceae family. It is a dimorphic single-celled yeast and an opportunistic pathogen. In the human body, it often appears as the yeast cell form when asymptomatic; when invading tissues and causing symptoms, it typically manifests as the hyphal form. Under normal circumstances, Candida in the human body exists as the yeast cell form and generally does not cause disease. However, under certain factors (such as diabetes, pregnancy, oral contraceptive use, antibiotics, and corticosteroid administration) that reduce the body's immunity or alter the local environment, Candida can proliferate extensively and develop into the hyphal form, invading tissues and causing pathological changes.

bubble_chart Pathogenesis

Candida is a conditional pathogenic microorganism. Whether it causes disease after invading the human body depends on the host's immune status as well as the quantity and virulence of the infecting strain. Conditions such as pregnancy, diabetes, oral contraceptive use, long-term use of broad-spectrum antibiotics, corticosteroids, and immunosuppressants can lower the body's immunity and alter the vaginal environment, making it easier to induce Candida infection.

1. Adhesion ability; adhesion is directly proportional to virulence, with Candida albicans exhibiting the strongest adhesion among Candida species;
2. Dimorphic morphology: during infection, C. albicans often appears in the hyphal form, which is more virulent than the yeast form;
3. Toxins: polysaccharide toxins on the fungal cell surface and another substance known as "candidal toxin" may contribute to pathogenicity;
4. Cell surface components;
5. Extracellular enzymes: C. albicans can secrete enzymes such as lysophospholipase, phospholipase, and extracellular acidic protease (CAP). Among these, CAP is the most important. CAP not only hydrolyzes proteins but also breaks down common bletilla tuber collagen, enhancing the adhesion function of C. albicans.

C. albicans infection begins with adhesion to the host's epithelial cells, followed by the formation of infection foci under the influence of the aforementioned pathogenic factors. Adhesion to epithelial cells occurs because the host cell membrane surface contains adhesion receptors for C. albicans, namely fucose and N-acetylglucosamine. The cell wall of C. albicans possesses multiple adhesion mediators, the most important of which are mannan-protein complexes (M-P) and chitin. Chitin is a three-dimensional polymer formed by (1-3, 1-6) β-glucan and N-acetylglucosamine compounds. The cell wall of C. albicans also contains adhesion receptors for components such as fibrinogen and fibronectin. These components are widely distributed in vascular walls, sites of inflammation, and wound healing, exhibiting strong adhesiveness. Upon binding to C. albicans, they bridge the adhesion between the fungus and host cells, making it easier for C. albicans to adhere to and invade the host.

Candidal balanoposthitis: Commonly seen in individuals with redundant prepuce and a history of unclean sexual intercourse. The penile prepuce and glans show grade I erythema, with white cheesy patches on the inner prepuce and coronal sulcus of the glans. The glans may exhibit pinpoint-sized pale red papules. If the outer prepuce and scrotum are involved, scaly erythema may be observed. Involvement of the navicular fossa can lead to symptoms such as frequent urination and dysuria. Local symptoms may include a burning sensation and cutaneous pruritus. For those with candidal hypersensitivity, penile itching and burning sensation may occur within hours after unclean intercourse, accompanied by erythema of the prepuce and glans. Occasionally, fulminant edematous balanoposthitis may occur, primarily characterized by significant edema of the penile prepuce, intense itching, and superficial ulcers.

Candidal vulvovaginitis; Vaginal cutaneous pruritus and increased leucorrhea are prominent features of this condition. Local cutaneous pruritus may lead to swelling of the labia minora due to scratching, along with epidermal erosion, scratch marks, and pustules. Vaginal secretions become thick, cheesy, or curd-like with a foul odor. Symptoms may also include vaginal pain, irritation, and dyspareunia. Examination may reveal white pseudomembranes on the vaginal mucosal membrane, which, upon detachment, may leave erythema or erosions, along with vaginal wall congestion and edema. Candida can be isolated from the vagina of some asymptomatic healthy women, but this does not necessarily cause vaginitis. Factors such as pregnancy, oral contraceptive use, antibiotic therapy, diabetes, or wearing tight, non-breathable underwear may serve as predisposing factors for vaginitis.

bubble_chart Auxiliary Examination

1. Direct Microscopic Examination: For females, use a long sterile cotton swab to collect secretions from the vagina, cervix, or the milky-white thin membrane on the vaginal wall. For males, scrape scales from the surface of lesions on the glans penis, coronal sulcus, or foreskin as the specimen. Process the specimen with 10% potassium hydroxide or saline on a slide, and observe under the microscope for clusters of oval spores and pseudohyphae. The presence of abundant pseudohyphae indicates that the Candida is in a pathogenic stage, which is more significant for diagnosis.

2. Staining Examination: Gram staining, Congo red staining, or PAS staining can also be used, followed by microscopic examination. The positive rate of these methods is higher than that of direct microscopy. With Gram staining, spores and pseudohyphae appear blue; with Congo red and PAS staining, they appear red.

3. Culture Isolation: For patients with negative smear results, Candida culture can be performed. Under aseptic conditions, inoculate the specimen onto Sabouraud's medium (usually using the tube culture method). When inoculating, slightly scratch the slant surface of the tube medium and inoculate 2–3 spots per tube, with two tubes per specimen. Incubate the medium at 37°C for 24–48 hours, then observe for the growth of abundant milky-white colonies. Use an inoculation needle to pick a small amount of the colony for smear preparation, and examine directly or after staining. The presence of numerous budding spores can preliminarily diagnose Candida infection.

4. Immunodiffusion or latex agglutination tests can be used to detect Candida albicans antibodies.

bubble_chart Diagnosis

1. Candidal vulvovaginitis: vulvovaginal cutaneous pruritus, pain or stabbing pain; ① cheesy or bean dregs-like leucorrhea; ② vaginal examination reveals pseudomembrane on the vaginal wall; ③ positive fungal test.

2. Candidal balanoposthitis: ① history of unclean sexual intercourse or redundant prepuce; ② erythema of the prepuce and glans, papules on the glans, cheesy patches on the inner prepuce or coronal sulcus; ③ candidal hypersensitivity or fulminant edematous balanoposthitis may present with their respective typical symptoms; ④ positive fungal test.

bubble_chart Treatment Measures

Asymptomatic individuals may not require treatment. Remove predisposing factors, abstain from sexual intercourse during treatment, and simultaneously treat the spouse or sexual partner.

(1) Vulvovaginal Candidiasis (VCC)

Mainly treated with topical medications. Imidazole antifungals are more effective than nystatin. After treatment with imidazole antifungals, symptoms disappear in 80–90% of patients, and Candida cultures turn negative.

1. Rinse the vulva with a 3% sodium bicarbonate solution or irrigate the vagina with a 1:5000 gentian violet solution, once or twice daily.
2. Insert nystatin suppositories or imidazole antifungal suppositories, such as clotrimazole, miconazole, econazole, or butoconazole, one per night deep into the vagina, for 1–2 weeks.
3. For vulvitis, apply topical imidazole antifungal preparations, such as clotrimazole cream, miconazole cream, econazole cream, ketoconazole cream, or bifonazole cream.
4. If the above methods yield poor results, the following oral medications may be used:
   1. Ketoconazole, 400 mg daily for 5 days;
   2. Fluconazole, a single 150 mg oral dose;
   3. Itraconazole, 200 mg twice daily (one-day regimen) or 200 mg once daily for 3 days.

(2) Recurrent Vulvovaginal Candidiasis (RVVC)

Clinically common, although certain predisposing factors can be identified, the epidemiology and objective factors influencing its occurrence remain unclear. There is currently no optimal treatment regimen. However, preventive or maintenance systemic antifungal therapy can effectively reduce the recurrence rate of RVVC. All RVVC cases should be confirmed by culture before initiating maintenance therapy.

1. Itraconazole, orally, 200 mg on the first day of menstruation, continued for 6 menstrual cycles, followed by a 200 mg daily, 3-day course.
2. Ketoconazole, orally, 100 mg daily for 6 months.

(3) Candidal Balanitis

Rinse the affected area with normal saline or a 0.1% rivanol solution, 2–3 times daily. After rinsing, apply 1–2% gentian violet solution or the aforementioned imidazole creams. For individuals with redundant prepuce, circumcision should be performed after cure to prevent recurrence. Those with concurrent urethritis may take ketoconazole, fluconazole, or itraconazole orally.

bubble_chart Prevention

1. Keep the vulva clean, wash frequently, change underwear often, and keep the area dry. Avoid using topical corticosteroid hormones.

2. Take showers instead of baths.

3. The patient's spouse or sexual partner should also be examined and treated, and sexual activity should be avoided during treatment. Avoid extramarital sexual behavior.

4. Actively prevent and manage the aforementioned predisposing factors.

bubble_chart Differentiation

This disease is mainly differentiated from trichomonal vaginitis and male non-gonococcal urethritis caused by trichomonads.

1. Trichomonal vaginitis is characterized by increased vaginal discharge that is foamy, sometimes serous or purulent, with a foul odor. It may also involve urethritis, cystitis, cervicitis, infection of the paraurethral glands and Bartholin's glands, and occasionally pyelonephritis. Symptoms such as dysuria, hematuria, and nocturia may occur. Vaginal examination reveals congested cervix, congested and edematous vaginal walls with petechiae, presenting a characteristic strawberry-like appearance. Trichomonas vaginalis can be detected.

2. Male non-gonococcal urethritis presents with milder symptoms than gonorrhea, manifesting as urethral cutaneous pruritus, discomfort, or dysuria, and may have purulent discharge. It can also lead to cystitis, prostatitis, or epididymitis. Trichomonads can be detected in the urethral discharge.