Subcutaneous Mycoses PDF

Lecture 5: The Subcutaneous Mycoses These are chronic, localized infections of the skin and subcutaneous tissue following the traumatic implantation of the aetiologic agent. Infection may arise following the wounding of the skin and the introduction of spores or hyphae of the fungus. The causa...

Lecture 5: The Subcutaneous Mycoses These are chronic, localized infections of the skin and subcutaneous tissue following the traumatic implantation of the aetiologic agent. Infection may arise following the wounding of the skin and the introduction of spores or hyphae of the fungus. The causative fungi are all soil saprophytes of regional epidemiology. These mycoses are rare and confined mainly to tropical regions.These include: Sporotrichosis,Chromoblastomycosis,Mycetoma and Phaeohyphomycosis 1--Sporotrichosis:- Is a disease caused by the infection of the fungus Sporothrix schenckii. This fungal disease usually affects the skin, although other rare forms can affect the lungs, joints, bones, and even the brain. Because roses (conidia or spores) can spread the disease, it is one of a few diseases referred to as rose-thorn or rose-gardeners' disease. Because S. schenckii is naturally found in soil, hay, sphagnum moss, and plants, it usually affects farmers, gardeners, and agricultural workers. It enters through small cuts (wounds)and abrasions in the skin to cause the infection. In case of sporotrichosis affecting the lungs, the fungal spores enter through the respiratory pathways. Sporotrichosis can also be acquired from handling cats with the disease; it is an occupational hazard for veterinarians.  Pathophysiology :Infection with the dimorphic soil fungus S schenckii is usually acquired from organic matter through cutaneous inoculation. The mycosis has also been transmitted from animals through bites or scratches. Cats have been responsible for cases among veterinarians and for a large outbreak in Rio de Janeiro, Brazil. See the image below. Colony morphology (left).Conidiophores and conidia of S schenckii Types of sporotrichosis. 1- Cutaneous (skin) sporotrichosis is the most common form of the infection. It usually occurs on a person’s hand or the arm after they have been handling contaminated plant matter. Lesions often start out as a painless nodule which soon become palpable and ulcerate often discharging a serous or purulent fluid. Importantly, lesions remain localized around the initial site of implantation.  2- Pulmonary (lung) sporotrichosis is very rare but can happen after someone breathes in fungal spores from the environment. 3- Disseminated sporotrichosis occurs when the infection spreads to another part of the body, such as the bones, joints, or the central nervous system. This form of sporotrichosis usually affects people who have weakened immune systems, such as people with HIV infection. Laboratory diagnosis 1. Clinical material: A tissue biopsy is the best specimen. 2. Direct Microscopy: Tissue sections should be stained using PAS digest, Grocott's methenamine silver (GMS) or Gram stain.  Section from a fixed cutaneous lesion showing round Periodic Acid-Schiff (PAS) positive budding yeast-like cells Sporothrix schenckii is a dimorphic fungus and this is the typical yeast-like form seen in tissue. Interpretation: Look for small narrow base budding yeast cells (2-5um). Note they are often present in very low numbers and may be difficult to find. PAS and GMS stains are essential. 3. Culture: Clinical specimens should be inoculated onto primary isolation media, like Sabouraud's dextrose agar and Brain heart infusion agar supplemented with 5% sheep blood. Interpretation: A positive culture from a biopsy should be considered significant.  Management: Cutaneous lesions respond well to saturated potassium iodide [4-6 ml three time a day for 2-4 months], however itraconazole [400 mg/day] and terbinafine [250 mg twice daily] have both proved to be effective, although treatment times may be long. Ideally, treatment needs to be maintained for at least a month after clinical cure is achieved. Local heat has also been shown to improve cutaneous lesions. Extracutaneous forms of sporotrichosis may need a combination of antifungal treatment with Amphotericin B or itraconazole together with surgical debridement. 2- Chromoblastomycosis: Description: A mycotic infection of the cutaneous and subcutaneous tissues characterised by the development in tissue of dematiaceous (brown-pigmented), planate-dividing, rounded sclerotic bodies. Infections are caused by the traumatic implantation of fungal elements into the skin and are chronic, slowly progressive and localised. Tissue proliferation usually occurs around the area of inoculation producing crusted, verrucose, wart-like lesions. World-wide distribution but more common in bare footed populations living in tropical regions.  Aetiological agents include various dematiaceous hyphomycetes associated with decaying vegetation or soil, especially Phialophora verrucosa, Fonsecaea pedrosoi, F. compacta and Cladophialophora carrionii. Clinical manifestations: Lesions of chromoblastomycosis are most often found on exposed parts of the body and usually start a small scaly papules or nodules which are painless but may be itchy. Satellite lesions may gradually arise and as the disease develops rash-like areas enlarge and become raised irregular plaques that are often scaly or verrucose. In long standing infections, lesions may become tumorous and even cauliflower-like in appearance.  Chronic verrucous chromoblastomycosis of the hand due to Cladophialophora carrionii. : Laboratory diagnosis 1. Clinical Material: Skin scrapings and/or biopsy. 2. Direct Microscopy: (a) Skin scrapings should be examined using 10% KOH and Parker ink or calcofluor white mounts; (b) Tissue sections should be stained using H&E, PAS digest, and Grocott's methenamine silver (GMS).  Interpretation: The presence in tissue of brown pigmented, planate-dividing, rounded sclerotic bodies from a patient with supporting clinical symptoms should be considered significant. Remember direct microscopy or histopathology does not offer a specific identification of the causative agent. Note: direct microscopy of tissue is necessary to differentiate between chromoblastomycosis and phaeohyphomycosis where the tissue morphology of the causative organism is mycelial Skin scrapings from a patient with chromoblastomycosis mounted in 10% KOH and Parker ink solution showing characteristic brown pigmented, planate-dividing, rounded sclerotic bodies.  H&E stained section showing characteristic dark brown sclerotic cells which divide by binary fission and not by budding. Note all agents of chromoblastomycosis form these sclerotic bodies in tissue. Culture: Clinical specimens should be inoculated onto primary isolation media, like Sabouraud's dextrose agar. Interpretation: The dematiaceous hyphomycetes involved are well recognised as environmental fungi, therefore a positive culture from a non-sterile specimen, such as sputum or skin, needs to be supported by clinical history and direct microscopic evidence in order to be considered significant. Culture identification is the only reliable means of distinguishing these fungi.  Cultures of the aetiologic agents of chromoblastomycosis are typically olivaceous-black with a suede-like surface 4. Identification: Culture characteristics and microscopic morphology are important, especially conidial morphology, the arrangement of conidia on the conidiogenous cell and the morphology of the conidiogenous cell. Cellotape flag and/or slide culture preparations are recommended. Causative agents: Cladophialophora carrionii, Fonsecaea pedrosoi, Phialophora verrucosa  Management The treatment of chromoblastomycosis has been exceedingly difficult. Successful surgical excision requires the removal of a margin of uninfected tissue to prevent local dissemination. Flucytosine with or without thiabendazole has been extensively used in the past. However both itraconazole [400 mg/day] and terbinafine [500 mg/ day] for 6 to 12 months have been used successfully for the treatment of chromoblastomycosis. 3- Phaeohyphomycosis Description: A mycotic infection of humans and lower animals caused by a number of dematiaceous (brown-pigmented) fungi where the tissue morphology of the causative organism is mycelial. This separates it from other clinical types of disease involving brown-pigmented fungi where the tissue morphology of the organism is a grain (mycotic mycetoma) or sclerotic body (chromoblastomycosis).  The etiological agents include various dematiaceous hyphomycetes especially species of Exophiala, Phialophora, Wangiella, Bipolaris, Exserohilum, Cladophialophora , Phaeoannellomyces, Aureobasidium, Cladosporium, Curvularia and Alternaria. Clinical manifestation A. Subcutaneous phaeohyphomycosis: Subcutaneous infections occur worldwide, usually following the traumatic implantation of fungal elements from contaminated soil, thorns or wood splinters. Exophiala jeanselmei and Wangiella dermatitidisare the most common agents and cystic lesions occur most often in adults. Occasionally, overlying verrucous lesions are formed, especially in the immunosuppressed patient.  Subcutaneous phaeohyphomycosis caused by Exophiala jeanselmei. 1. Clinical material: Skin scrapings and/or biopsy; sputum and bronchial washings; cerebrospinal fluid, pleural fluid and blood; tissue biopsies from various visceral organs and indwelling catheter tips. 2. Direct Microscopy: (a) Skin scrapings, sputum, bronchial washings and aspirates should be examined using 10% KOH and Parker ink or calcofluor white mounts; (b) Exudates and body fluids should be centrifuged and the sediment examined using either 10% KOH and Parker ink or calcofluor white mounts, (c) Tissue sections should be stained using H&E, PAS digest, and Grocott's methenamine silver (GMS).  Interpretation: The presence of brown pigmented, branching septate hyphae in any specimen, from a patient with supporting clinical symptoms should be considered significant. Biopsy and evidence of tissue invasion is of particular importance. Remember direct microscopy or histopathology does not offer a specific identification of the causative agent. Note: direct microscopy of tissue is necessary to differentiate between chromoblastomycosis which is characterized by the presence in tissue of brown pigmented, planate-dividing, rounded sclerotic bodies and phaeohyphomycosis where the tissue morphology of the causative organism is mycelial. Culture of Cladosporium showing typical brown, olivaceous black or black colony colour for a dematiaceous hyphomycete.  Culture of Phialophora showing typical brown, olivaceous black or black colony colour for a dematiaceous hyphomycete. Mycetoma Description: A mycotic infection of humans and animals caused by a number of different fungi and actinomycetes characterized by draining sinuses, granules and tumefaction. The disease results from the traumatic implantation of the aetiologic agent and usually involves the cutaneous and subcutaneous tissue, fascia and bone of the foot or hand. Sinuses discharge serosanguinous fluid containing the granules which vary in size, colour and degree of hardness, depending on the aetiologic species, and are the hallmark of mycetoma. World-wide distribution but most common in bare-footed populations living in tropical or subtropical regions. Aetiological agents include Madurella, Acremonium, Pseudallescheria, Exophiala, Leptosphaeria, Curvularia, Fusarium, Aspergillus etc.  Mycetoma showing numerous draining sinuses. There is destruction of bone, distortion of the foot, and hyperplasia at the.openings of the sinus tracts Laboratory diagnosis 1. Clinical Material: Tissue biopsy or excised sinus, serosanguinous fluid containing the granules which vary in size, colour and degree of hardness, depending on the aetiologic species. 2. Direct Microscopy: Serosanguinous fluid containing the granules should be examined using either 10% KOH and Parker ink or calcofluor white mounts, and tissue sections should be stained using H&E, PAS digest, and Grocott's methenamine silver (GMS).  3-Interpretation: The presence of white to yellow or black pigmented grains, from a patient with supporting clinical symptoms should be considered significant. Biopsy and evidence of tissue invasion is of particular importance. Remember direct microscopy or histopathology does not offer a specific identification of the causative agent. 4. Culture: Clinical specimens should be inoculated onto primary isolation media, like Sabouraud's dextrose agar. 5. Identification: Characteristic clinical, microscopic and culture features. Causal agents: Acremonium sp., Aspergillus nidulans, Madurella grisea, Madurella mycetomatis, Scedosporium apiospermum. Treatment is difficult due to inability of drugs to infiltrate lesions. Combination of medicine (Amphotericin B)and surgery is the best for Eumycotic mycetoma: