Notes
Superficial & Cutaneous Mycoses
Sections
Superficial and Cutaneous Mycoses
KEY PHYLA
Basidiomycota:
Specifically, species of Malassezia, which are yeast that colonize the superficial layers of the skin and hair.
Because they do not invade or destroy living tissues, they generally do not trigger an immune response.
Infections common in warm, moist environments.
Ascomycota:
Dermatophytes are fungal pathogens that can invade the skin and cause dermatophytoses, such as ringworm.
Dermatophytic species come from three genera:
Trichophyton, Epidermophyton, and Microsporum.
These molds infect keratin of the skin, hair, and nails; because they cause damage to the tissues, they trigger an immune response.
These fungi cause mycoses called tineas, aka, ringworm.
They are acquired from contact with infected soil, animals, or other humans.
Laboratory diagnosis:
KOH (potassium hydroxide) testing, in which skin scrapings and KOH are viewed under microscope.
Calcofluor white stain is also used to detect fungi in samples; comprises fluorescent stain with affinity for the chitin in fungal cell walls.
Treatments:
When necessary, treatments for superficial and cutaneous mycoses involves topical and/or oral antifungals, in addition to good hygiene.
Pityriasis versicolor
Sometimes called tinea versicolor.
Caused by species of the Malassezia genus.
Malassezia comprises cells and some short hyphae; some authors describe their appearance as looking like "spaghetti and meatballs."
Young adults in warm, moist environments are most likely to develop pityriasis versicolor.
Fungi are spread via human to human contact.
Lesions appear as either hypo- or hyper-pigmented, and typically appear on the upper body, face, and neck.
Tinea nigra
Tinea nigra is caused by the fungus Hortaea werneckii.
Comprises septate hyphae and budding cells.
Tinea nigra is most common in children and young adults in tropical and subtropical climates.
Manifests as patches of small dark dots, typically on the palms of the hands and soles of the feet.
White piedra
White piedra (piedra means "stone") is caused by species of Trichosporon, which are yeasts that colonize the hair shaft.
Individuals in tropical and subtropical areas are most likely to have white piedra.
Look for soft white or cream-colored nodules on the hair shafts.
Black piedra
Black piedra is caused by the yeast Piedra hortae, which colonizes the hair and scalp of individuals in tropical areas.
Look for firm dark nodules in the hair.
Tineas
Commonly referred to as Ringworm.
Caused by dermatophytic fungi.
The tineas are named for their location on the body, as follows:
Tinea capitis develops on the scalp, especially of children, and is associated with alopecia, scaling, and cervical and suboccipital lymphadenopathy.
Tinea barbae is ringworm that occurs in areas of facial hair.
Tinea corporis is ringworm that appears on the trunk or extremities; it produces red rings with scaly skin and is pruritic (itchy).
Tinea cruris, aka, jock itch, is most common in adolescent and young males; it produces a rash on the upper thighs, but typically does not involve the scrotum.
Tinea pedis, aka, athlete's foot, can involve all aspects of the feet:
Interdigital is the most common, and involves the skin between the toes
Moccasin tinea pedis is chronic and involves the sides and soles of the feet
Vesicular tinea pedis is characterized by inflammation with vesicles and lesions
Tinea unguium is a fungal infection of the nails (thus, it is a type of onychomycosis).
Be aware that opportunistic fungi that infect the skin, such species of Candida, are discussed in separate tutorials.
References
Borda, Luis J., and Tongyu C. Wikramanayake. "Seborrheic Dermatitis and Dandruff: A Comprehensive Review." Journal of Clinical and Investigative Dermatology 3, no. 2 (December 2015). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4852869/.
Elewski, Boni E., Heather R. Haley, and Courtney M. Robbins. "The Use of 40% Urea Cream in the Treatment of Moccasin Tinea Pedis." Cutis 73, no. 5 (May 2004): 355–57.
Ely, John W., Sandra Rosenfeld, and Mary Seabury Stone. "Diagnosis and Management of Tinea Infections." American Family Physician 90, no. 10 (November 15, 2014): 702–10.
Gaitanis, Georgios, Prokopios Magiatis, Markus Hantschke, Ioannis D. Bassukas, and Aristea Velegraki. "The Malassezia Genus in Skin and Systemic Diseases." Clinical Microbiology
Reviews 25, no. 1 (January 1, 2012): 106–41. https://doi.org/10.1128/CMR.00021-11.
Murray, P. R., Rosenthal K.S., & Pfaller, M.A. Medical Microbiology. 8th ed. Elsevier, 2016.
Tyring, Stephen K., Omar Lupi, and Ulrich Hengge R. Tropical Dermatology E-Book. Elsevier Health Sciences, 2016. https://play.google.com/store/books/details?id=_GdjDQAAQBAJ&rdid=book-_GdjDQAAQBAJ&rdot=1&source=gbs_atb.
Images:
al, Ran Yuping et. Left: A 27-Year-Old Man Presented in Our Clinic with Extensive Erythema and Scaly for 6 Months. Right: Under SEM, Abundant of 3–5 Μm in Diameter Grapes-like Spherical Malassezia Spores (S) with Budding Daughter Cell, with Collar Structure around the Budding, and Banana-like Haphae (H). 2016. [1]. https://commons.wikimedia.org/wiki/File:Malassezia_spores_2.jpg.
"Hortaea Werneckii." Wikipedia, September 1, 2018.
https://en.wikipedia.org/w/index.php?title=Hortaea_werneckii&oldid=857547427.
Nódulos de Piedra Negra En El Cabello Infectado Por El Hongo Piedraia Hortae. December 4, 2017. https://openi.nlm.nih.gov/detailedresult.php?img=PMC2938571_IJT-1-100-g015&req=4. https://commons.wikimedia.org/wiki/File:Piedra_Negra_Micosis.png.
Malassezia furfur in skin.
http://phil.cdc.gov/phil_images/20030610/22/PHIL_3938_lores.jpg. https://commons.wikimedia.org/wiki/File:Malassezia_furfur_in_skin_scale_from_a_patient_with_tinea_versicolor_PHIL_3938_lores.jpg.
Joanmrl. Español: Enfermedad Micótica Por El Hongo Trichosporon Beigelii. December 4, 2017. Own work. https://commons.wikimedia.org/wiki/File:Piedra_Blanca_Micosis.jpg.
Manuel, Arbotti Juan. Español: Tiña Unguis En Paciente de Sexo Masculino de 55 Años de Edad.English: Onychomycosis: 55 Year Old Male Pacient. July 6, 2011. Own work. https://commons.wikimedia.org/wiki/File:Tinea_ungui%C3%BCm_o_%22Ti%C3%B1a_unguis%22.jpg.
"Yeartinfection.JPG - Wikipedia." Accessed September 21, 2018. https://it.m.wikipedia.org/wiki/File:Yeartinfection.JPG.
Oger, Grook Da. Français : Pityriasis Versicolor / Tinea Versicolor. July 22, 2011. Own work. https://commons.wikimedia.org/wiki/File:Pityriasis_versicolor_frontal_retouche.jpg.
"Public Domain Picture | This Image Shows a Patient with Ringworm of the Scalp, 'Tinea Capitis', Due to an Infection Caused by Microsporum Canis. | ID: 13544853612058 | PublicDomainFiles.Com." Accessed September 21, 2018. http://www.publicdomainfiles.com/show_file.php?id=13544853612058.
Tinea Nigra Is a Cutaneous Hiperpigmetation Macula Caused by the Fungus: Hortaea Werneckii. January 1, 2009. http://www.actasdermo.org/imatges/103/103v100n07/grande/103v100n07-13140517fig3.jpg. https://commons.wikimedia.org/wiki/File:Tinea_nigra.jpg.