'Clues' for the histological diagnosis of tinea: how reliable are they?

Tinea Incognito: Challenges in Diagnosis and Management

Tinea incognito is a dermatophyte infection with atypical features, due to the use of topical or systemic steroids or other immunosuppressive medications. Delayed diagnosis, spread of the infection to critical body surfaces, resistance to antifungal drugs, and increased costs due to prolonged hospitalization and multiple treatment regimens often complicate tinea incognito. It can affect individuals of all ages and genders, but it is more common in children. Atypical clinical appearance often necessitates differentiation from other diseases such as eczema, seborrheic dermatitis, lupus erythematosus, psoriasis, or other non-fungal skin conditions. The treatment of tinea incognito usually involves discontinuation of topical steroids or other immunosuppressive medications. Preventive measures and management of the underlying fungal infection are necessary and can be achieved with antifungal drugs. Patients should wear loose cotton clothes, use boiling water for laundry, and iron their clothing before wearing them. Additionally, they should avoid sharing bed linens, towels, clothes, and shoes. This review aims to raise awareness of tinea incognito among health practitioners, provide tips for detecting the disorder, include it in the differentials, and evaluate the available diagnostic procedures.

The role of eosinophils in the differential diagnosis of inflammatory skin diseases

Eosinophils are known to be present in inflammatory skin diseases, but their diagnostic utility is not well established. Upon review of the published status of lesional eosinophils, several categories were identified. 1) Lesional eosinophils highly characteristic such that, in their absence, the pathologist may question the diagnosis. These include arthropod bite reactions and scabies, urticarial dermatitis, and other eosinophilic dermatoses. 2) Lesional eosinophils rare or absent, such that, in their presence, the pathologist may question the diagnosis. These include pityriasis lichenoides, graft versus host disease, and connective tissue disorders. 3) Lesional eosinophils variable and, while in some cases expected, are not required for diagnosis. These include drug reactions, atopic dermatitis and allergic contact dermatitis. 4) Lesional eosinophils variable and not expected but may be seen to a limited extent. These include lichen planus and psoriasis.

Updates and Proposed Diagnostic Approach to Psoriasiform Dermatoses

Psoriasiform dermatoses represent a wide array of skin diseases commonly encountered by clinicians and pathologists. While they may present a diagnostic challenge, thorough observation coupled with proper interpretation of subtle additional clinical or histopathologic features provide clues to the correct diagnosis. In this review, we provide updates on emerging entities and develop a systemic approach to establish the pathologic diagnosis, with emphasis on the importance of clinicopathologic correlation.

Current Topics in Dermatophyte Classification and Clinical Diagnosis

Dermatophytes are highly infectious fungi that cause superficial infections in keratinized tissues in humans and animals. This group of fungi is defined by their ability to digest keratin and encompasses a wide range of species. Classification of many of these species has recently changed due to genetic analysis, potentially affecting clinical diagnosis and disease management. In this review, we discuss dermatophyte classification including name changes for medically important species, current and potential diagnostic techniques for detecting dermatophytes, and an in-depth review of Microsporum canis, a prevalent zoonotic dermatophyte. Fungal culture is still considered the “gold standard” for diagnosing dermatophytosis; however, modern molecular assays have overcome the main disadvantages of culture, allowing for tandem use with cultures. Further investigation into novel molecular assays for dermatophytosis is critical, especially for high-density populations where rapid diagnosis is essential for outbreak prevention. A frequently encountered dermatophyte in clinical settings is M. canis, which causes dermatophytosis in humans and cats. M. canis is adapting to its primary host (cats) as one of its mating types (MAT1-2) appears to be going extinct, leading to a loss of sexual reproduction. Investigating M. canis strains around the world can help elucidate the evolutionary trajectory of this fungi.

Tinea Incognito—A Great Physician Pitfall

Tinea incognito is a dermatophyte infection exacerbated after inadequate administration of topical or systemic glucocorticoids. A 57-year-old man presented to the Department of Dermatology due to skin lesions persisting for one month. He reported having recently worked under hot conditions, in tight clothing, which caused sweating. Later, he noticed erythematous–exfoliative lesions in his groins and on the buttocks. He presented to the general practitioner who diagnosed him with eczema and prescribed clobetasole ointment. Since the skin lesions became more severe, he presented to the Department of Dermatology. On the physical examination, extensive erythematous–infiltrative lesions were observed in the area of medial, lateral, and posterior surface of both thighs and buttocks. Pustules were also present. Suspicion of tinea incognito was raised, and direct mycological examination and culture confirmed the presence of dermatophytes. The patient was prescribed topical terbinafine and oral itraconazole. Tinea incognito may be challenging to diagnose because the clinical presentation is relatively nonspecific and definitive culture or histopathological diagnosis such as by microscopic sample examination to identify fungal elements is not universally available. Every doctor has to keep in mind the fact that tinea may be a great mimicker of other dermatoses and to not prescribe medications without microscopic confirmation of tinea, and refer patients for dermatological consultation in case of doubt.

PAS and GMS utility in dermatopathology: Review of the current medical literature

The American Society of Dermatopathology has established an Appropriate Use Criteria (AUC) Committee with the intention of establishing evidence-based recommendations regarding the appropriateness of various ancillary tests commonly utilized by dermatopathologists. Periodic acid Schiff (PAS) and Grocott (or Gomori) methenamine silver (GMS) stains represent some of the most commonly employed ancillary tests in dermatopathology. The utility of these tests was targeted for evaluation by the AUC. This literature review represents a comprehensive evaluation of available evidence for the utility of PAS and/or GMS staining of skin and nail biopsies. In concert with expert opinion, these data will be incorporated into future recommendations by the AUC for PAS and GMS staining in routine dermatopathology practice.

In situ immune response in human dermatophytosis: possible role of Langerhans cells (CD1a+) as a risk factor for dermatophyte infection

Dermatophytosis is a cutaneous mycosis caused by a plethora of keratinophilic fungi, but Trichophyton rubrum is the most common etiological agent. Despite its high prevalence worldwide, little is known about the host defense mechanisms in this infection, particularly the in situ immune response. Using an immunohistochemistry approach, we investigated the density of CD1a+, factor XIIIa+ and CD68+ cells in the skin of dermatophytosis patients. Langerhans cells (CD1a+ cells) were significantly decreased in the epidermis of patients, both in affected and unaffected areas. In the dermis, however, no differences in the density of macrophages (CD68+ cells) and dermal dendrocytes (factor XIIIa+ cells) were observed. These results suggest that the decreased number of Langerhans cells may be a risk factor for development of dermatophytosis.

Can Routine Histopathology Distinguish Between Vulvar Cutaneous Candidosis and Dermatophytosis?

OBJECTIVES

This study aimed to determine if vulvar cutaneous candidosis and dermatophytosis can be distinguished by routine histopathology.

MATERIALS AND METHODS

Twenty-four cases of periodic acid-Schiff-stained vulvar biopsies with a diagnosis of cutaneous mycosis were reviewed and histopathological characteristics on both periodic acid-Schiff and hematoxylin and eosin were recorded. Data were collected on age, clinical impression, microbiological results, and treatment, and all specimens underwent multiplex polymerase chain reaction analysis.

RESULTS

The mean age was 60 years, and all but 3 women had at least 1 risk factor for mycosis including 15 (62.5%) with lichen sclerosus and/or planus managed with topical corticosteroids. A clinical suspicion of tinea or candidosis was documented in 12 (50%) of the cases. Vulvovaginal swabs showed Candida species in 9 women; one skin scraping was positive for Trichophyton rubrum. Microbiology was not obtained in 8 patients, 5 had a negative swab, and 1 had negative skin scrapings. No histopathological or morphological features distinguished Candida species from dermatophytes. Organisms appeared as basophilic structures in the stratum corneum in 15 (62.5%) hematoxylin and eosin-stained slides. Polymerase chain reaction results were positive for Candida species in 5 (21%) and for dermatophytes in 3 (13%), negative in 13, and unassessable in 3 cases.

CONCLUSIONS

Vulvar cutaneous candidosis and dermatophytosis cannot be reliably distinguished by routine histopathology or specific polymerase chain reaction. A high index of suspicion combined with adequate microbiological testing remains the best approach to differentiating between the 2, which impacts on counseling, treatment, and prognosis.

Polycyclic Annular Lesion Masquerading as Lupus Erythematosus and Emerging as Tinea Faciei Incognito

Tinea incognito is a dermatophytic infection induced by immunosuppressive agents that lacks the classic features of a typical fungal infection. Although the treatment of tinea incognito is simple and relatively easy, its clinical manifestation varies and can masquerade as various skin disorders, causing misdiagnosis and thus preventing prompt and appropriate treatment. Here, we report an interesting case of tinea incognito occurring after topical steroid administration in an immunosuppressed patient with dermatitis artefacta. A 40-year-old female patient who had been taking systemic glucocorticoid for 4 years for chronic inflammatory demyelinating polyneuropathy presented with itching multiple erythematous erosive lesions on the face and upper chest for 2 months. Initial biopsy produced nonspecific findings. The skin lesion was aggravated and became polycyclic and erythematous; after azathioprine was added, her chronic inflammatory demyelinating polyneuropathy became aggravated. A second biopsy confirmed hyphae in the cornified layer. Complete remission was achieved after admonishing oral terbinafine and topical amorolfine.