Clinicomycological Evaluation and Therapeutic Management of Secondary Malassezia pachydermatis Dermatitis Associated with Generalized Demodicosis in Dog
Aug 2026· Journal of Advances in Microbiology· Vol 26, pp. 43-50· 0 citations
TL;DR
Generalised demodicosis may predispose dogs to secondary Malassezia overgrowth through disruption of the skin barrier and alteration of local immune responses, while antifungal susceptibility testing may assist in selecting appropriate therapy.
Abstract
Aim: To describe the clinicomycological, cytological, antifungal susceptibility and therapeutic findings of secondary Malassezia pachydermatis dermatitis associated with generalised demodicosis in a Pug and to emphasise the importance of an integrated diagnostic and therapeutic approach.
Presentation of case: An 8-year-old female Pug weighing 8.5 kg was presented with a 6-month history of generalised pruritus, alopecia, greasy seborrhoea, hyperpigmentation, lichenification and characteristic foul odour. Generalised demodicosis was diagnosed based on deep skin scrapings. Cutaneous cytology using Diff-Quik and New Methylene Blue staining revealed numerous budding yeast cells suggestive of Malassezia spp. Fungal culture followed by phenotypic characterisation confirmed the isolate as Malassezia pachydermatis, while antifungal susceptibility testing by the disc diffusion method supported the selection of itraconazole for systemic therapy. The dog was treated with an isoxazoline-based acaricide for generalised demodicosis, along with oral itraconazole and topical chlorhexidine–miconazole shampoo. Supportive treatment was also provided. The treatment resulted in the resolution of the cutaneous lesions and progressive hair regrowth, with complete clinical recovery. The dog was followed for one month after completion of treatment, during which no recurrence of dermatological lesions was observed.
Discussion: Generalised demodicosis may predispose dogs to secondary Malassezia overgrowth through disruption of the skin barrier and alteration of local immune responses. A combination of parasitological, cytological and mycological investigations facilitates a definitive diagnosis, while antifungal susceptibility testing may assist in selecting appropriate therapy. Concurrent treatment of the underlying demodicosis and secondary Malassezia dermatitis is important for achieving clinical resolution and reducing the risk of recurrence.
Conclusion: This case highlights the usefulness of integrated clinicomycological, parasitological and cytological investigations in the diagnosis and management of canine Malassezia dermatitis associated with generalised demodicosis. Early recognition and concurrent treatment of both conditions resulted in complete clinical resolution, with no recurrence observed during the one-month follow-up period.
Cutaneous protothecosis is a rare opportunistic infection caused by achlorophyllous algae of the genus Prototheca and often poses a diagnostic challenge because of marked clinical polymorphism and the absence of pathognomonic features. We report a case of cutaneous protothecosis in a 78-year-old woman with a long history of pruritic skin eruptions and a history of uncontrolled long-term use of topical corticosteroids. During prior evaluation, systemic connective tissue disease and a paraneoplastic etiology of the cutaneous process were excluded. The key diagnostic step was a skin biopsy with histopathological examination, which demonstrated a lichenoid pattern combined with productive granulomatous inflammation in the dermis, raising suspicion of an infectious dermatosis and prompting additional special stains. Ziehl–Neelsen staining was negative, excluding mycobacterial infection. Periodic acid–Schiff (PAS) staining revealed PAS-positive structures. Culture of shave-biopsy material on Sabouraud dextrose agar yielded Prototheca wickerhamii, confirming the diagnosis of protothecosis. The patient was started on itraconazole 100 mg twice daily, with gradual regression of skin lesions and improvement of subjective symptoms.
N. Burtseva, I. Makhinenko, T. Melnikova et al.· Vestnik Dermatologii i Vener...· 0 citations
Background: Malassezia folliculitis (MF) is an inflammatory disorder of the hair follicles caused by overgrowth of lipophilic Malassezia yeasts. It typically presents as monomorphic, pruritic follicular papules and pustules on seborrheic areas and is often misdiagnosed as acne vulgaris or bacterial folliculitis.
Case report: A 38-year-old man returning from Spain presented with pruritic papules and pustules on the back, chest, shoulders, and face. No comedones were present. A routine bacterial culture was negative, and previous antibiotic and anti-acne treatment had been ineffective. Wood's lamp examination showed yellow-green fluorescence, and direct microscopy with methylene blue and Gram staining demonstrated abundant Malassezia yeasts. Treatment with clotrimazole cream, ketoconazole 2% shampoo, and fluconazole 150 mg weekly for four weeks resulted in clinical resolution.
Conclusion: Malassezia folliculitis should be considered in monomorphic, pruritic, treatment-resistant acneiform eruptions. Direct microscopy is a rapid confirmatory method, and antifungal therapy is generally effective, although recurrence may require maintenance treatment.
L. Zisova, Gergana Vazheva· Journal of IMAB· 0 citations
Fusarium solani (F. solani), a ubiquitous environmental fungus and common phytopathogen, rarely causes cutaneous infections in humans-particularly in immunocompromised individuals, where it may lead to severe or disseminated disease with poor prognosis. We report a 60-year-old male with myelofibrosis on long-term ruxolitinib therapy, presenting with progressive cutaneous granulomas on the left thumb (duration: 6 weeks) and back (duration: 2 weeks). The diagnosis of cutaneous fusariosis was established based on clinical presentation, combined with fungal culture, morphological characterization and molecular identification of the pathogen from lesion exudates, crusts and excised tissue specimens obtained from both lesions. Multimodal therapy was initiated: empirical itraconazole combined with 5-aminolevulinic acid photodynamic therapy (ALA-PDT) for the thumb lesion, and surgical excision for the back lesion. Notably, although antifungal susceptibility later revealed itraconazole resistance, the patient showed marked improvement during combination therapy with itraconazole and PDT. Based on susceptibility results (terbinafine MIC < 0.03 μg/mL), the antifungal regimen was switched to terbinafine plus PDT. Complete remission was achieved with no recurrence at 6 month follow up. This case suggests that the multimodal regimen-combining systemic antifungal therapy, local ALA-PDT and surgical excision-may be an effective strategy for managing refractory cutaneous F. solani infection. However, the independent therapeutic contribution of ALA-PDT cannot be determined from a single case report.
Yiping Liang, Yahui Feng, Huiyu Zhang et al.· Photodiagnosis and Photodyna...· 0 citations
An unusual instance of chromoblastomycosis caused by F. pedrosoi in a woman from South Kerala with a preceding history of a leech bite is described, highlighting the importance of combining clinical examination, histopathology, fungal culture, and molecular sequencing for accurate diagnosis and effective management of this rare and chronic fungal infection.
Ashna Ajimsha, Neeraja C. K., Kiran Subhash· Journal Of Vocational Health...· 0 citations
BACKGROUND: Pityriasis rubra pilaris (PRP, Devergie’s disease) is a rare chronic inflammatory skin disease belonging to the group of papulosquamous dermatoses, clinically characterized by erythematous papules and plaques with frequent development of erythroderma. Erythroderma can also be observed in psoriasis and cutaneous T-cell lymphoma (mycosis fungoides). Based on a previously conducted retrospective clinical and epidemiological study of patients with the erythrodermic form of PRP, psoriasis, and mycosis fungoides for the period 2014–2024 at the V.A. Rakhmanov Clinic of Skin and Venereal Diseases (see Part 1), it can be concluded that these diseases may have similar clinical manifestations. However, the histological signs of erythroderma are often non-specific, which complicates diagnosis verification. Furthermore, when mycosis fungoides is suspected, additional diagnostic methods and the development of a differential diagnostic algorithm for diseases presenting with erythroderma are required.
AIM: To conduct a comparative analysis of clinical, anamnestic, histological, and immunohistochemical features of the erythrodermic form of PRP, psoriasis, and mycosis fungoides based on literature data and the results of our study, with the subsequent development of a differential diagnostic algorithm for erythroderma.
METHODS: The study involved an analysis of the literature using the PubMed, Scopus, and Google Scholar databases for the period 2000–2025, as well as the results of a clinical and epidemiological study conducted at the V.A. Rakhmanov Clinic of Skin and Venereal Diseases, University Clinical Hospital No. 2, Sechenov University, for the period 2014–2024.
RESULTS: According to the literature, erythroderma develops in a significant proportion of patients with PRP, whereas in psoriasis it is observed in 1–2.25% of cases, and in late-stage mycosis fungoides – in 17.3% of patients. PRP is characterized by a bimodal age incidence peak: the first peak occurs in childhood, the second in adulthood. The onset of the disease is usually acute or subacute. The rash typically shows caudal spread with possible spontaneous regression. Key differential diagnostic features of PRP included salmon-colored plaques that coalesce to develop erythroderma, the presence of "islands" of spared skin, palmoplantar keratoderma, and alopecia.
It was previously believed that a positive response to systemic retinoids combined with an absent or minimal response to phototherapy could be considered an important clinical diagnostic criterion favoring PRP in the differential diagnosis from psoriasis and mycosis fungoides. However, resistance and insufficient response to systemic retinoid therapy are currently being reported with increasing frequency.
CONCLUSION: Differential diagnosis of the erythrodermic form of PRP, psoriasis, and mycosis fungoides requires an integrated approach, based on clinical and anamnestic data analysis and the results of laboratory and instrumental diagnostic methods. The proposed algorithm for the differential diagnosis of diseases presenting with erythroderma serves as a valuable tool for accurate and rapid diagnosis verification and the prompt selection of targeted therapy.
O. Olisova, N. Teplyuk, E. Grekova et al.· Russian Journal of Skin and...· 0 citations
An unusual instance of chromoblastomycosis caused by F. pedrosoi in a woman from South Kerala with a preceding history of a leech bite is described, highlighting the importance of combining clinical examination, histopathology, fungal culture, and molecular sequencing for accurate diagnosis and effective management of this rare and chronic fungal infection.
Ashna Ajimsha, C. Study, Kasus Chromoblastomycosis et al.· 0 citations
