Skin: structure, function, and biological significance

Cutaneous Candidiasis: A Case Study

Candidiasis

This case study involves a 35-year-old woman diagnosed with candidiasis of the inner thighs. The goal of this report is to provide the patient with information about the most likely cause of her condition and how best to resolve the infection. In order to accomplish this goal a review of Candida pathogenesis will be presented first.

Candida Pathogenesis

Members of the Candida genus, in particular C. albicans, can be detected in the oral cavities of 75% of the general population (Mayer, Wilson, & Hube, 2013). This mostly commensal microbe colonizes oral, vaginal, gastrointestinal, anal, and cutanous locations (Raz-Pasteur, Ullmann, & Berdicevsky, 2011). Candida species are commensal in health people and rarely cause any problems, but in persons who suffer from mild medical conditions with impaired immunity the commensal relationship can quickly evaporate and turn pathogenic (Mayer, Wilson, & Hube, 2013). For example, Candida is responsible for a fourth of all hospital acquired infections in the U.S. And nearly half result in death.

Some of the main risk factors for development of pathogenic Candida infections are an HIV infection, dentures, and immune senescence in the elderly (Mayer, Wilson, & Hube, 2013). Other risk factors include diabetes, antibiotic use, oral contraception use, pregnancy, hormone therapy, neutropenia, and gastrointestinal trauma. The latter two risk factors can lead to systemic candidiasis with high mortality rates. By comparison, cutaneous and mucosal candidiasis is relatively benign. For example, most women will develop a vulvovaginal Candida infection during their lifetime with a recurrence rate close to 50%. Up to 8% of these women will develop at least four vulvovaginal infections per year.

C. albicans, the most common pathogenic fungal microbe infecting humans, can change shape and function depending on the environment (Mayer, Wilson, & Hube, 2013). The most common forms detected in human infections are ovoid-shaped budding yeast and parallel-walled hyphae, with the former predominating in low pH and the latter at high pH. Hyphae growth is also promoted by normal body temperatures, carbon dioxide, and starvation. The yeast form has been attributed to pathogenic dissemination, while the hyphae form is seen most often in invasive infections.

The mechanisms underlying candidiasis involve a number of steps from adhering to an epithelial surface to invading host cells (Mayer, Wilson, & Hube, 2013). Adhesion is mediated by several surface molecules that allow yeast and hyphae cells to adhere to each other, non-biotic surfaces, and host cells. Hyphae express surface proteins that bind to E- and N-cadherin on epithelial cells, which promote passive endocytosis into the host cells. Hyphae are also capable of actively invading a host cells through an unknown mechanism, probably involving the secretion of proteases. During the infection process C. albicans fulfills its nutritional needs at the expense of the surrounding tissue and can actively control the pH of its surrounding environment to its advantage. The structural typology of the epithelial surface will also influence the direction of hyphal growth, in a process called thigmotropism. Skin folds and ridges are some of the topological features that promote thigmotropism. Once an invasive infection is established the hyphae can quickly mount defenses against host immunity. For example, during an ex-vivo experiment with human mucosa C. albicans readily formed biofilms within five days (Raz-Pasteur, Ullmann, & Berdicevsky, 2011), thereby providing protection against endogenous immune factors and exogenous antibiotics (Mayer, Wilson, & Hube, 2013).

Case Study Evaluation

The 35-year-old woman who is the subject of this case study was diagnosed with candidiasis of the intertrigenous regions of the inner thighs. One concern expressed by the patient is whether the infection represents a sexually transmitted disease. Candida species can be transmitted through sexual contact between two persons (Mansur, Aydingoz, & Artunkal, 2012), so this concern is valid; however, the fungal species responsible for the infection could just as easily have come from the patient herself. The patient should be counseled about safe sex, but the primary concern should be whether the patient is suffering from any of the risk factors associated with candidiasis.

Mansur and colleagues (2012) review all of the risk factors for follicular candidiasis when reporting a case study. These risk factors include a tropical climate (excessive sweating), history of yeast infections, diabetes mellitus, drug abuse history, alcoholism, immunosuppressive drug use, antibiotic use, hypothyroidism, agranulocytosis, and malignant tumors. Many of these risk factors, however, produce their own sets of symptoms that can include a fever, headache, fatigue, arthralgia, myalgia, costochondral arthritis, and tissue damage. The case study under consideration here only reports candidiasis and not any other signs or symptoms. To preclude possible contributing comorbidities a number of laboratory tests should be performed, including complete blood count, hematocrit, blood biochemistry, TSH, urinalysis, hepatitis B and C, and HIV.

In the absence of any other contributing factors, the candidiasis of the inner thighs is probably due to a breakdown of the protective epithelial barrier. The case study by Mansure and colleages (2012) attributed the facial follicular candidiasis to skin abrasions caused by shaving during particularly hot and humid weather, rather than to reported orogenital sexual counters; although, the treating physicians could not definitively exclude the sexual encounters as a possible contributing factor.