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21.4: Mycoses of the Skin and Eyes - Biology

21.4: Mycoses of the Skin and Eyes - Biology


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Learning Objectives

  • Identify the most common fungal pathogens associated with cutaneous and subcutaneous mycoses
  • Compare the major characteristics of specific fungal diseases affecting the skin

Many fungal infections of the skin involve fungi that are found in the normal skin microbiota. Some of these fungi can cause infection when they gain entry through a wound; others mainly cause opportunistic infections in immunocompromised patients. Other fungal pathogens primarily cause infection in unusually moist environments that promote fungal growth; for example, sweaty shoes, communal showers, and locker rooms provide excellent breeding grounds that promote the growth and transmission of fungal pathogens.

Fungal infections, also called mycoses, can be divided into classes based on their invasiveness. Mycoses that cause superficial infections of the epidermis, hair, and nails, are called cutaneous mycoses. Mycoses that penetrate the epidermis and the dermis to infect deeper tissues are called subcutaneous mycoses. Mycoses that spread throughout the body are called systemic mycoses.

Tineas

A group of cutaneous mycoses called tineas are caused by dermatophytes, fungal molds that require keratin, a protein found in skin, hair, and nails, for growth. There are three genera of dermatophytes, all of which can cause cutaneous mycoses: Trichophyton, Epidermophyton, and Microsporum. Tineas on most areas of the body are generally called ringworm, but tineas in specific locations may have distinctive names and symptoms (see Table (PageIndex{1}) and Figure (PageIndex{1})). Keep in mind that these names—even though they are Latinized—refer to locations on the body, not causative organisms. Tineas can be caused by different dermatophytes in most areas of the body.

Table (PageIndex{1}): Tineas and locations
Some Common Tineas and Location on the Body
Tinea corporis (ringworm)Body
Tinea capitis (ringworm)Scalp
Tinea pedis (athlete’s foot)Feet
Tinea barbae (barber’s itch)Beard
Tinea cruris (jock itch)Groin
Tinea unguium (onychomycosis)Toenails, fingernails

Dermatophytes are commonly found in the environment and in soils and are frequently transferred to the skin via contact with other humans and animals. Fungal spores can also spread on hair. Many dermatophytes grow well in moist, dark environments. For example, tinea pedis (athlete’s foot) commonly spreads in public showers, and the causative fungi grow well in the dark, moist confines of sweaty shoes and socks. Likewise, tinea cruris (jock itch) often spreads in communal living environments and thrives in warm, moist undergarments.

Tineas on the body (tinea corporis) often produce lesions that grow radially and heal towards the center. This causes the formation of a red ring, leading to the misleading name of ringworm recall the Clinical Focus case in The Eukaryotes of Microbiology.

Several approaches may be used to diagnose tineas. A Wood’s lamp (also called a black lamp) with a wavelength of 365 nm is often used. When directed on a tinea, the ultraviolet light emitted from the Wood’s lamp causes the fungal elements (spores and hyphae) to fluoresce. Direct microscopic evaluation of specimens from skin scrapings, hair, or nails can also be used to detect fungi. Generally, these specimens are prepared in a wet mount using a potassium hydroxide solution (10%–20% aqueous KOH), which dissolves the keratin in hair, nails, and skin cells to allow for visualization of the hyphae and fungal spores. The specimens may be grown on Sabouraud dextrose CC (chloramphenicol/cyclohexamide), a selective agar that supports dermatophyte growth while inhibiting the growth of bacteria and saprophytic fungi (Figure (PageIndex{2})). Macroscopic colony morphology is often used to initially identify the genus of the dermatophyte; identification can be further confirmed by visualizing the microscopic morphology using either a slide culture or a sticky tape prep stained with lactophenol cotton blue.

Various antifungal treatments can be effective against tineas. Allylamine ointments that include terbinafine are commonly used; miconazole and clotrimazole are also available for topical treatment, and griseofulvin is used orally.

Exercise (PageIndex{1})

Why are tineas, caused by fungal molds, often called ringworm?

Cutaneous Aspergillosis

Another cause of cutaneous mycoses is Aspergillus, a genus consisting of molds of many different species, some of which cause a condition called aspergillosis. Primary cutaneous aspergillosis, in which the infection begins in the skin, is rare but does occur. More common is secondary cutaneous aspergillosis, in which the infection begins in the respiratory system and disseminates systemically. Both primary and secondary cutaneous aspergillosis result in distinctive eschars that form at the site or sites of infection (Figure (PageIndex{3})). Pulmonary aspergillosis will be discussed more thoroughly in Respiratory Mycoses).

Primary cutaneous aspergillosis usually occurs at the site of an injury and is most often caused by Aspergillus fumigatus or Aspergillus flavus. It is usually reported in patients who have had an injury while working in an agricultural or outdoor environment. However, opportunistic infections can also occur in health-care settings, often at the site of intravenous catheters, venipuncture wounds, or in association with burns, surgical wounds, or occlusive dressing. After candidiasis, aspergillosis is the second most common hospital-acquired fungal infection and often occurs in immunocompromised patients, who are more vulnerable to opportunistic infections.

Cutaneous aspergillosis is diagnosed using patient history, culturing, histopathology using a skin biopsy. Treatment involves the use of antifungal medications such as voriconazole (preferred for invasive aspergillosis), itraconazole, and amphotericin B if itraconazole is not effective. For immunosuppressed individuals or burn patients, medication may be used and surgical or immunotherapy treatments may be needed.

Exercise (PageIndex{2})

Identify the sources of infection for primary and secondary cutaneous aspergillosis.

Candidiasis of the Skin and Nails

Candida albicans and other yeasts in the genus Candida can cause skin infections referred to as cutaneous candidiasis. Candida spp. are sometimes responsible for intertrigo, a general term for a rash that occurs in a skin fold, or other localized rashes on the skin. Candida can also infect the nails, causing them to become yellow and harden (Figure (PageIndex{4})).

Candidiasis of the skin and nails is diagnosed through clinical observation and through culture, Gram stain, and KOH wet mounts. Susceptibility testing for anti-fungal agents can also be done. Cutaneous candidiasis can be treated with topical or systemic azole antifungal medications. Because candidiasis can become invasive, patients suffering from HIV/AIDS, cancer, or other conditions that compromise the immune system may benefit from preventive treatment. Azoles, such as clotrimazole, econazole, fluconazole, ketoconazole, and miconazole; nystatin; terbinafine; and naftifine may be used for treatment. Long-term treatment with medications such as itraconazole or ketoconazole may be used for chronic infections. Repeat infections often occur, but this risk can be reduced by carefully following treatment recommendations, avoiding excessive moisture, maintaining good health, practicing good hygiene, and having appropriate clothing (including footwear).

Candida also causes infections in other parts of the body besides the skin. These include vaginal yeast infections (see Fungal Infections of the Reproductive System) and oral thrush (see Microbial Diseases of the Mouth and Oral Cavity).

Exercise (PageIndex{3})

What are the signs and symptoms of candidiasis of the skin and nails?

Sporotrichosis

Whereas cutaneous mycoses are superficial, subcutaneous mycoses can spread from the skin to deeper tissues. In temperate regions, the most common subcutaneous mycosis is a condition called sporotrichosis, caused by the fungus Sporothrix schenkii and commonly known as rose gardener’s disease or rose thorn disease (recall Case in Point: Every Rose Has Its Thorn). Sporotrichosis is often contracted after working with soil, plants, or timber, as the fungus can gain entry through a small wound such as a thorn-prick or splinter. Sporotrichosis can generally be avoided by wearing gloves and protective clothing while gardening and promptly cleaning and disinfecting any wounds sustained during outdoor activities.

Sporothrix infections initially present as small ulcers in the skin, but the fungus can spread to the lymphatic system and sometimes beyond. When the infection spreads, nodules appear, become necrotic, and may ulcerate. As more lymph nodes become affected, abscesses and ulceration may develop over a larger area (often on one arm or hand). In severe cases, the infection may spread more widely throughout the body, although this is relatively uncommon.

Sporothrix infection can be diagnosed based upon histologic examination of the affected tissue. Its macroscopic morphology can be observed by culturing the mold on potato dextrose agar, and its microscopic morphology can be observed by staining a slide culture with lactophenol cotton blue. Treatment with itraconazole is generally recommended.

Exercise (PageIndex{4})

Describe the progression of a Sporothrix schenkii infection.

MYCOSES OF THE SKIN

Cutaneous mycoses are typically opportunistic, only able to cause infection when the skin barrier is breached through a wound. Tineas are the exception, as the dermatophytes responsible for tineas are able to grow on skin, hair, and nails, especially in moist conditions. Most mycoses of the skin can be avoided through good hygiene and proper wound care. Treatment requires antifungal medications. Figure (PageIndex{5}) summarizes the characteristics of some common fungal infections of the skin.

Key Concepts and Summary

  • Mycoses can be cutaneous, subcutaneous, or systemic.
  • Common cutaneous mycoses include tineas caused by dermatophytes of the genera Trichophyton, Epidermophyton, and Microsporum. Tinea corporis is called ringworm. Tineas on other parts of the body have names associated with the affected body part.
  • Aspergillosis is a fungal disease caused by molds of the genus Aspergillus. Primary cutaneous aspergillosis enters through a break in the skin, such as the site of an injury or a surgical wound; it is a common hospital-acquired infection. In secondary cutaneous aspergillosis, the fungus enters via the respiratory system and disseminates systemically, manifesting in lesions on the skin.
  • The most common subcutaneous mycosis is sporotrichosis (rose gardener’s disease), caused by Sporothrix schenkii.
  • Yeasts of the genus Candida can cause opportunistic infections of the skin called candidiasis, producing intertrigo, localized rashes, or yellowing of the nails.

Contributor

  • Nina Parker, (Shenandoah University), Mark Schneegurt (Wichita State University), Anh-Hue Thi Tu (Georgia Southwestern State University), Philip Lister (Central New Mexico Community College), and Brian M. Forster (Saint Joseph’s University) with many contributing authors. Original content via Openstax (CC BY 4.0; Access for free at https://openstax.org/books/microbiology/pages/1-introduction)


21.4: Mycoses of the Skin and Eyes - Biology

Many fungal infections of the skin involve fungi that are found in the normal skin microbiota. Some of these fungi can cause infection when they gain entry through a wound others mainly cause opportunistic infections in immunocompromised patients. Other fungal pathogens primarily cause infection in unusually moist environments that promote fungal growth for example, sweaty shoes, communal showers, and locker rooms provide excellent breeding grounds that promote the growth and transmission of fungal pathogens.

Fungal infections, also called mycoses, can be divided into classes based on their invasiveness. Mycoses that cause superficial infections of the epidermis, hair, and nails, are called cutaneous mycoses. Mycoses that penetrate the epidermis and the dermis to infect deeper tissues are called subcutaneous mycoses. Mycoses that spread throughout the body are called systemic mycoses.


Microbiome and skin biology

Purpose of review: The skin is home to a diverse milieu of bacteria, fungi, viruses, bacteriophages, and archaeal communities. The application of culture-independent approaches has revolutionized the characterization of the skin microbiome and have revealed a previously underappreciated phylogenetic and functional granularity of skin-associated microbes in both health and disease states.

Recent findings: The physiology of a given skin-niche drives the site-specific differences in bacterial phyla composition of healthy skin. Changes in the skin microbiome have consistently been associated with atopic dermatitis. In particular, Staphylococcus aureus overgrowth with concomitant decline in Staphylococcus epidermidis is a general feature associated with atopic dermatitis and is not restricted to eczematous lesions. Changes in fungal species are now also being described. Changes in the composition and metabolic activity of the gut microbiota are associated with skin health.

Summary: We are now beginning to appreciate the intimate and intricate interactions between microbes and skin health. Multiple studies are currently focused on the manipulation of the skin or gut microbiome to explore their therapeutic potential in the prevention and treatment of skin inflammation.


Cutaneous Aspergillosis

Another cause of cutaneous mycoses is Aspergillus , a genus consisting of moulds of many different species, some of which cause a condition called aspergillosis . Primary cutaneous aspergillosis, in which the infection begins in the skin, is rare but does occur. More common is secondary cutaneous aspergillosis, in which the infection begins in the respiratory system and disseminates systemically. Both primary and secondary cutaneous aspergillosis result in distinctive eschars that form at the site or sites of infection (Figure 22.28). Pulmonary aspergillosis will be discussed more thoroughly in Respiratory Mycoses).

Figure 22.28. (a) Eschar on a patient with secondary cutaneous aspergillosis. (b) Micrograph showing a conidiophore of Aspergillus. [Credit a: modification of work by Santiago M, Martinez JH, Palermo C, Figueroa C, Torres O, Trinidad R, Gonzalez E, Miranda Mde L, Garcia M, Villamarzo G credit b: modification of work by U.S. Department of Health and Human Services]

Primary cutaneous aspergillosis usually occurs at the site of an injury and is most often caused by Aspergillus fumigatus or Aspergillus flavus. It is usually reported in patients who have had an injury while working in an agricultural or outdoor environment. However, opportunistic infections can also occur in health-care settings, often at the site of intravenous catheters, venipuncture wounds, or in association with burns, surgical wounds, or occlusive dressing. After candidiasis, aspergillosis is the second most common hospital-acquired fungal infection and often occurs in immunocompromised patients, who are more vulnerable to opportunistic infections.

Cutaneous aspergillosis is diagnosed using patient history, culturing, histopathology using a skin biopsy. Treatment involves the use of antifungal medications such as voriconazole (preferred for invasive aspergillosis), itraconazole , and amphotericin B if itraconazole is not effective. For immunosuppressed individuals or burn patients, medication may be used and surgical or immunotherapy treatments may be needed.


Roseola and Fifth Disease

The viral diseases roseola and fifth disease are somewhat similar in terms of their presentation, but they are caused by different viruses. Roseola, sometimes called roseola infantum or exanthem subitum (“sudden rash”), is a mild viral infection usually caused by human herpesvirus-6 (HHV-6) and occasionally by HHV-7. It is spread via direct contact with the saliva or respiratory secretions of an infected individual, often through droplet aerosols. Roseola is very common in children, with symptoms including a runny nose, a sore throat, and a cough, along with (or followed by) a high fever (39.4 ºC). About three to five days after the fever subsides, a rash may begin to appear on the chest and abdomen. The rash, which does not cause discomfort, initially forms characteristic macules that are flat or papules that are firm and slightly raised some macules or papules may be surrounded by a white ring. The rash may eventually spread to the neck and arms, and sometimes continues to spread to the face and legs. The diagnosis is generally made based upon observation of the symptoms. However, it is possible to perform serological tests to confirm the diagnosis. While treatment may be recommended to control the fever, the disease usually resolves without treatment within a week after the fever develops. For individuals at particular risk, such as those who are immunocompromised, the antiviral medication ganciclovir may be used.

Fifth disease (also known as erythema infectiosum) is another common, highly contagious illness that causes a distinct rash that is critical to diagnosis. Fifth disease is caused by parvovirus B19, and is transmitted by contact with respiratory secretions from an infected individual. Infection is more common in children than adults. While approximately 20% of individuals will be asymptomatic during infection, [2] others will exhibit cold-like symptoms (headache, fever, and upset stomach) during the early stages when the illness is most infectious. Several days later, a distinct red facial rash appears, often called “slapped cheek” rash (Figure 3). Within a few days, a second rash may appear on the arms, legs, chest, back, or buttocks. The rash may come and go for several weeks, but usually disappears within seven to twenty-one days, gradually becoming lacy in appearance as it recedes.

Figure 3. (a) Roseola, a mild viral infection common in young children, generally begins with symptoms similar to a cold, followed by a pink, patchy rash that starts on the trunk and spreads outward. (b) Fifth disease exhibits similar symptoms in children, except for the distinctive “slapped cheek” rash that originates on the face.

In children, the disease usually resolves on its own without medical treatment beyond symptom relief as needed. Adults may experience different and possibly more serious symptoms. Many adults with fifth disease do not develop any rash, but may experience joint pain and swelling that lasts several weeks or months. Immunocompromised individuals can develop severe anemia and may need blood transfusions or immune globulin injections. While the rash is the most important component of diagnosis (especially in children), the symptoms of fifth disease are not always consistent. Serological testing can be conducted for confirmation.

Think about It


Contents

Mycoses are traditionally divided into superficial, subcutaneous, or systemic, where infection is deep, more widespread and involving internal body organs. [3] [11] They can affect the nails, vagina, skin and mouth. [13] Some types such as blastomycosis, cryptococcus, coccidioidomycosis and histoplasmosis, affect people who live or visit certain parts of the world. [13] Others such as aspergillosis, pneumocystis pneumonia, candidiasis, mucormycosis and talaromycosis, tend to affect people who are unable to fight infection themselves. [13] Mycoses might not always conform strictly to the three divisions of superficial, subcutaneous and systemic. [3] Some superficial fungal infections can cause systemic infections in people who are immunocompromised. [3] Some subcutaneous fungal infections can invade into deeper structures, resulting in systemic disease. [3] Candida albicans can live in people without producing symptoms, and is able to cause both mild candidiasis in healthy people and severe invasive candidiasis in those who cannot fight infection themselves. [3] [7]

ICD-11 codes Edit

  • 1F20 Aspergillosis
  • 1F21 Basidiobolomycosis
  • 1F22 Blastomycosis
  • 1F23 Candidosis
  • 1F24 Chromoblastomycosis
  • 1F25 Coccidioidomycosis
  • 1F26 Conidiobolomycosis
  • 1F27 Cryptococcosis
  • 1F28 Dermatophytosis
  • 1F29 Eumycetoma
  • 1F2A Histoplasmosis
  • 1F2B Lobomycosis
  • 1F2C Mucormycosis
  • 1F2D Non-dermatophyte superficial dermatomycoses
  • 1F2E Paracoccidioidomycosis
  • 1F2F Phaeohyphomycosis
  • 1F2G Pneumocystosis
  • 1F2H Scedosporiosis
  • 1F2J Sporotrichosis
  • 1F2K Talaromycosis
  • 1F2L Emmonsiosis

Superficial mycoses Edit

Superficial mycoses include candidiasis in healthy people, common tinea of the skin, such as tinea of the body, groin, hands, feet and beard, and malassezia infections such as pityriasis versicolor. [3] [7]


Sporotrichosis

Rodrigo Almeida-Paes , . Rosely M. Zancopé-Oliveira , in Reference Module in Life Sciences , 2020

Abstract

Sporotrichosis is a subcutaneous mycosis that fulfills the criteria to be recognized as a tropical neglected disease. In last years, several advances on the genus Sporothrix and on the infection were achieved. The current state of art of the etiological agents of sporotrichosis, including taxonomic classification, morphology, physiology, biology, ecology, and virulence, has changed sporotrichosis demographics, morbidity, clinical forms, immunology, diagnosis, and treatment. This article will focus on these aspects, as well as on the advances that are still missing, to fight this disease properly.


What is mycoses of the skin?

Mycosis is a fungal infection of animals, including humans. Inhalation of fungal spores or localized colonization of the skin may initiate persistent infections therefore, mycoses often start in the lungs or on the skin.

Additionally, what are the different types of mycoses? There are three general types of subcutaneous mycoses: chromoblastomycosis, mycetoma, and sporotrichosis. All appear to be caused by traumatic inoculation of the etiological fungi into the subcutaneous tissue.

Also question is, what is mycosis caused by?

Mycosis, plural Mycoses, in humans and domestic animals, a disease caused by any fungus that invades the tissues, causing superficial, subcutaneous, or systemic disease. Subcutaneous infections, which extend into tissues and sometimes into adjacent structures such as bone and organs, are rare and often chronic.

What are subcutaneous mycoses?

Subcutaneous mycoses are a group of fungal diseases produced by a heterogeneous group of fungi that infect the skin, subcutaneous tissue, and in some cases the underlying tissues and organs.


Fungal Infections

Fungal Peritonitis

Fungal infections of the peritoneal cavity are usually due to Candida spp. They have become increasingly recognized, paralleling the increased numbers of patients undergoing continuous ambulatory peritoneal dialysis (infection incidence up to 20%) and gastrointestinal surgery (often associated with bacterial peritonitis and insidious in onset, but especially with anastomotic breakdown situations). Broad-spectrum antibiotic usage, parenteral nutrition, and immunosuppression are other important predisposing factors. Dissemination in patients who have candidal peritonitis in general is uncommon but occurs in up to 25% of cases of peritonitis secondary to intestinal perforation and following gastrointestinal surgery, with mortality as high as 80%. The presence of Candida in intraoperative specimens recovered from patients with intraabdominal perforations significantly relates to the risk of death. Fungal peritonitis is best managed with systemic antifungals and removal of the dialysis catheter if appropriate.


There's no way to avoid breathing in spores. But you can do a few things to lower your chances of mucormycosis. It's especially important if you have a health condition that raises your risk.

Stay away from areas with a lot of dust or soil, like construction or excavation sites. If you have to be in these areas, wear a face mask like an N95.

Avoid infected water. This can include floodwater or water-damaged buildings, especially after natural disasters like hurricanes or floods.

If you have a weakened immune system, avoid activities that involve dust and soil, like gardening or yard work. If you can't, protect your skin with shoes, gloves, long pants, and long sleeves. Wash cuts or scrapes with soap and water as soon as you can.

If you get mucormycosis, be sure to take your medications as directed. If side effects cause problems or the infection doesn't get better, let your doctor know right away.

Sources

CDC: “About Mucormycosis,” “People at Risk & Prevention,” “Mucormycosis statistics,” “Diagnosis and Testing for Mucormycosis,” “Symptoms of Mucormycosis,” “Treatment for Mucormycosis.”

National Organization for Rare Disorders: “Mucormycosis.”

Journal of Medical Cases: “Rhinocerebral Mucormycosis and COVID-19 Pneumonia.”


Watch the video: Fungal Infection Classification Part 3Mycology (May 2022).