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Background
Dermatophytes are fungal organisms which infect keratin of humans and animals. The results are unsightly and common infections of the skin, hair, and nails known popularly as ringworm and more precisely as tinea. The clinical appearance varies according to the site. On the skin, there is an erythematous, sometimes scaly patch. In the hair, broken shafts are common, sometimes associated with alopecia. On the nails, there is hyperkeratosis with dystrophy.
Microbiologists classify dermatophytes into three genera. The organisms vary in the site of infections and by geography. In addition to affecting humans and animals, they may live in the soil. In general, T. tonsurans and T. rubrum infections are increasing while M. canis and M. audouinii are declining. Dermatophytes more commonly transmitted by animals, such as M. audouinii, M. canis, T. verrucosum, and T. tonsurans are more common in children
OUTLINE
EPIDEMIOLOGY CHARACTERIZATION TINEA CAPITIS
J Am Acad Dermatol. 2006 Apr;54(4):622-6. Epub 2006 Feb 7. Abstract quote
BACKGROUND: The emerging outbreak of Trichophyton tonsurans infection among members of combat sports clubs in Japan during the last 4 years has become a serious public health problem. To overcome this outbreak, a survey for T. tonsurans infection in Japan may be essential.
OBJECTIVES: We sought to clarify the prevalence of T. tonsurans infection among members of combat sports clubs in Japan.
METHODS: We conducted a survey of members of participating combat sports clubs using a standardized questionnaire to assess background factors and using the hairbrush method to identify T. tonsurans infection. Statistical significance of the correlation between data from the questionnaire and the hairbrush culture results was determined.
RESULTS: We surveyed 1000 people (826 male) from 49 institutions and found 115 (11.5%) were positive for T. tonsurans infection revealed by the hairbrush method. Demographic factors associated with high positive rates (> or =20%) of the infection were familial T. tonsurans infection (20.0%), history of tinea corporis (24.2%), increased dandruff (32.1%), and concomitant tinea corporis (31.6%). Those with positive hairbrush culture results without current or previous tinea were considered asymptomatic carriers.
LIMITATIONS: The study population was limited to members of judo clubs all over Japan; they were asked to participate in this survey via the All Japan Judo Federation.
CONCLUSION: Infection of T. tonsurans appears to have spread widely among members of combat sports club in Japan. The questionnaire used in this study is a simple and useful tool to estimate epidemiology of this infection.
Tinea capitis in Cleveland: survey of elementary school students.Ghannoum M, Isham N, Hajjeh R, Cano M, Al-Hasawi F, Yearick D, Warner J, Long L, Jessup C, Elewski B.
Center for Medical Mycology and Mycology Reference Laboratory, Department of Dermatology, University Hospitals of Cleveland and Case Western Reserve University, 11100 Euclid Avenue, Cleveland, OH 44106-5028, USA
J Am Acad Dermatol 2003 Feb;48(2):189-93 Abstract quote BACKGROUND: Tinea capitis, a fungal infection of the scalp, is of increasing public health importance, and Trichophyton tonsurans has become the primary causative agent in North America.
OBJECTIVES: To determine the prevalence of dermatophyte-positive scalp cultures among elementary schoolchildren in Cleveland, Ohio, describe predisposing factors, and measure the antifungal susceptibility of isolates collected.
OBSERVATIONS: A total of 937 children from 8 Cleveland elementary schools were cultured for the presence of dermatophytes; 122 children (13%), all of whom were African American, had dermatophyte-positive cultures of the scalp. Sixty percent of cases were asymptomatic, indicating a carrier state. Race, scaling, and the use of anti-dandruff shampoo were associated with increased likelihood of infection. T tonsurans was the only organism isolated (except 1 Microsporum canis isolate). All isolates were susceptible to fluconazole, griseofulvin, itraconazole, and terbinafine.
CONCLUSIONS: T tonsurans was the predominant dermatophyte isolated. Further multicenter studies are needed to confirm the predominance of dermatophyte-positive scalp cultures among African American children and to determine modifiable and preventable risk factors.
GROSS APPEARANCE/
CLINICAL VARIANTSCHARACTERIZATION PENIS Penile dermatophytosis
Josie Pielop, etal.
J Am Acad Dermatol 2001;44:864-7 Abstract quote
Dermatophyte infections of the penis and scrotum are relatively rare compared with those involving the groin. Four cases of penile tinea due to Trichophyton rubrum are described. All patients had associated foci of fungal infection, but only one had crural involvement. Treatment with oral antifungal agents led to complete resolution of penile dermatophytosis.
Infection Clinical Appearance Organisms Favus Chronic infection of the scalp usually in childhood
Yellow crusts (scutula) on erythematous base
Alopecia commonT. schonleini
T. violaceum
M. gypseumKerion Boggy violaceous inflammatory area most common on scalp but occasionally other sites T. verrucosum
T. tonsuransMajocchi's granuloma Nodular plaquelike lesions
More common in females and on lower legs
Granulomatous perifolliculitisT. rubrum
M. canis
T. violaceum
T. tonsurans
T. mentagrophytesOnychomycosis Tinea barbae Infection of beard hairs on face T. rubrum
T. mentagrophytes
E. floccosumTinea capitis Infection of hair shafts of scalp T. tonsurans
T. violaceum
M. canis
M. audouiniiTinea corporis Infection of trunk T. rubrum
T. mentagrophytes
E. floccosumTinea cruris Jock itch
Almost always in malesT. rubrum
T. mentagrophytes
E. floccosumTinea faciei Facial erythema with scaling T. rubrum
T. mentagrophytes
T. tonsuransTinea nigra Tinea pedis Athlete's foot
Maceration and fissuring with sharply defined scaly lateral borderT. rubrum
T. mentagrophytes var. interdigitaleTinea versicolor (Pityriasis versicolor)
HISTOLOGICAL TYPES CHARACTERIZATION General The pathologist may perform a skin scraping and culture the scraping. A quick diagnosis can sometimes be achieved with a wet mount potassium hydroxide preparation (KOH prep). In this setting, the scrapings are placed on a slide and KOH is added with gentle heating. This dissolved the keratin (hair, keratinocytes) leaving the fungal organisms. A stain such as lactophenol blue may be added and the slide is examined under the microscope. Dermatophytes often take weeks to culture so a rapid diagnosis such as this is always helpful.
A skin biopsy may yield numerous histopathologic reaction patterns. One classic pattern is the presence of neutrophils within the stratum corneum. Other common patterns include compact orthokeratosis and a layer of compact orthokeratosis underlying normal orthokeratosis (sandwich sign). Occasionally the organisms may be seen with routine H and E stain, but commonly a special stain such as GMS or PAS can be used. Dermatophyte infections of the hair are termed endothrix if it invades the hair shaft and exothrix if it remains on the surface. Using a ultraviolet Wood's lamp, endothrix infections will not fluoresce as opposed to exothrix infections.
Intraepidermal neutrophils - a clue to dermatophytosis?Meymandi S, Silver SG, Crawford RI.
Division of Dermatology and Department of Pathology, University of British Columbia, Vancouver, Canada.
J Cutan Pathol 2003 Apr;30(4):253-5 Abstract quote BACKGROUND: Dermatophyte infections are occasionally diagnosed by histopathology. Spongiotic or psoriasiform features are typical but non-specific, and neutrophils may be present within the stratum corneum. Traditionally, this latter finding has been felt to be a diagnostic clue for dermatophytosis, and usually precipitates a periodic acid Schiff (PAS-D) stain to confirm the presence of hyphae in the stratum corneum. Our objective was to evaluate whether the presence of neutrophils within the stratum corneum is a sensitive or specific test for dermatophytosis.
METHODS: We performed a retrospective case-control study on 303 cases of spongiotic or psoriasiform dermatitides over a 35-month period. Hematoxylin and eosin (H&E) and PAS-D stains were utilized to identify intraepidermal neutrophils and fungi.
RESULTS: The sensitivity and specificity for diagnosing dermatophyte infection based upon neutrophils within the stratum corneum were 62 and 59%, respectively. The positive and negative predictive values in our population were 4 and 98%, respectively.
CONCLUSION: The histologic feature of neutrophils within the stratum corneum is neither sensitive nor specific in the diagnosis of dermatophytosis.
SPECIAL STAINS
IMMUNO-
PEROXIDASECHARACTERIZATION PAS
Department of Pathology, Government Medical College, Chandigarh, India.
BACKGROUND: The diagnosis of cutaneous fungal infection is usually made on clinical examination of the lesion and direct microscopic examination of skin scrapings with potassium hydroxide. Histopathological examination is rarely required to confirm dermatophytic infections. There is often a discord between the clinical and histopathological findings and many times clinical appearance can have a poor histopathological correlation.
METHODS: This retrospective study was carried out on all skin biopsies received in a period of 1 year. The clinical details of all cases were retrieved and slides were reviewed. Routine fungal staining periodic acid-Schiff (PAS) stain was performed in all cases.
RESULTS: Of 403 skin biopsies received in 1 year, material for further staining was available in 338. On re-examining the slides stained with PAS stain, fungi were identified in 34 cases (10%), of which fungal infection had been suspected clinically in five cases.
CONCLUSIONS: Use of routine stains like PAS can help to reach a correct diagnosis and initiate appropriate treatment. Fungal staining should be done in skin biopsies with non-specific clinical details and microscopic findings for best patient management.The periodic acid-Schiff stain in diagnosing tinea: should it be used routinely in inflammatory skin diseases?
Amina Al-Amiri, Vandana Chatrath, Jag Bhawan and Catherine M. StefanatoJ Cutan Pathol 2003;30:611-615 Abstract quote
Background: The clinical presentation of tinea is usually, but not always, characteristic. The purpose of this study was to determine whether the routine use of the periodic acid-Schiff (PAS) stain in inflammatory skin disorders is requisite for identifying clinically undiagnosed tinea cases and to ascertain whether there are histopathologic clues that suggest the diagnosis of a dermatophyte infection.Methods: Hematoxylin and eosin (H&E)-stained slides from 60 PAS-positive tinea cases were examined histologically by two observers. One observer, aware of the diagnosis of tinea, searched for hyphal elements and also recorded in detail epidermal, dermal, and follicular changes. The second observer, not aware of the diagnosis beforehand, reviewed the same slides, together with randomly mixed slides from 21 non-tinea cases, recording the same parameters as the first reviewer.
Results: Of the 60 cases of tinea, only 45% were diagnosed clinically. Histologic examination of H&E sections by the two observers disclosed the presence of hyphal elements in 68 and 45%, respectively. No significant histologic differences, except for the presence of hyphae, were observed between tinea and non-tinea cases.
Conclusions: The finding that only 57% of PAS-positive cases of tinea showed hyphal elements on H&E examination alone, together with no other differentiable histologic characteristics, lends strong support for the routine use of PAS-staining for inflammatory skin disorders.
DIFFERENTIAL DIAGNOSIS KEY DIFFERENTIATING FEATURES GENERAL Subtle intracorneal findings in inflammatory disorders: hyphae or not?
Szabo SK, Jaworsky C.
Departments of Dermatology, Case Western Reserve University, University Hospitals of Cleveland and MetroHealth Medical Center, Cleveland, OH, USA.
J Cutan Pathol. 2004 Oct;31(9):583-5. Abstract quote
Background: Spongiotic and lichenoid dermatitides are frequently stained with periodic acid-Schiff (PAS) stains to check for the presence of dermatophytes. PAS(+) structures without a septate morphology are often seen with lichenoid dermatitides, however, their nature has not been previously characterized.
Methods: Fifteen consecutive biopsies of lichenoid and five spongiotic dermatitides were stained with hematoxylin and eosin (H&E), PAS, and antibodies to CD1a.
Results: Twelve of 15 lichenoid and none of the five spongiotic dermatitis showed PAS(+) structures in the stratum corneum. Distinct septation or branching was not identified in these PAS(+) structures. Eleven of 15 from the lichenoid group, but none from the spongiotic group, showed CD1a(+) structures in the stratum corneum. This staining pattern suggests that the intracorneal structures represent the dendritic processes of Langerhans' cells (LCs) within the stratum corneum.
Conclusions: PAS(+) and CD1a(+) structures are present in the stratum corneum of lichenoid, but not in spongiotic, dermatitis. This study morphologically confirms extension of LC dendrites into the stratum corneum in lichenoid but not in spongiotic dermatitides.Henry JB. Clinical Diagnosis and Management by Laboratory Methods. Twentieth Edition. WB Saunders. 2001.
Rosai J. Ackerman's Surgical Pathology. Ninth Edition. Mosby 2004.
Sternberg S. Diagnostic Surgical Pathology. Fourth Edition. Lipincott Williams and Wilkins 2004.
Robbins Pathologic Basis of Disease. Seventh Edition. WB Saunders 2005.
DeMay RM. The Art and Science of Cytopathology. Volume 1 and 2. ASCP Press. 1996.
Weedon D. Weedon's Skin Pathology Second Edition. Churchill Livingstone. 2002
Fitzpatrick's Dermatology in General Medicine. 6th Edition. McGraw-Hill. 2003.
Weiss SW and Goldblum JR. Enzinger and Weiss's Soft Tissue Tumors. Fourth Edition. Mosby 2001.
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Last Updated December 18, 2008
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