Fungal Diseases - Mycoses

1. Fungal Diseases - Mycoses

2. Superficial Fungi • Pityriasis versicolora is a superficial mycosis which appears on the upper torso, arms, and abdomen as hyper/hypo pigmented macular lesions which scale leaving the area looking dry and chalky • Malassezia furfur is a lipophilic yeast which is part of the normal microflora of the skin; grows mostly a a yeast, but sometime produces a hyphal form. • grow in the skin is activated by certain predilecting factors like exposure to sunlight, etc. • organism is identified in KOH preparation of the white, chalky scales; organism appears a yeast cells among hypae

3. Cutaneous Fungi-Dermatophytes • Dermatophyte Fungi - are mold fungi which grow in tissues containing keratin; Thus, they are limited to skin, hair and nails. • cellular immune response to the presence of fungi in the skin evokes an inflammatory response often described as “ ringworm” or “tinea” • infections are often classified by the area affected; such as tinea capitis, tinea pedis, tinea manus, tinea ungium, etc. • there are three main dermatophyte genera which infect humans • Trichophyton • Epidermophyton • Microsporium • species within these genera are grouped based upon their source • anthropophilic humans • zoophilic animals • geophilic soil • dermatophytes are diagnosed by finding septate hypha and asexual(anamorphic) spores in the scraping of infected tissue. • specific identification of the fungi is made by culture

4. Subcutaneous Fungi- Mycosis • Lymphocutaneous Sporotrichosis nodular and ulcerative lesions which develop along the lymph channels which drain the primary site of inoculation; when the lymph gland is infected, the fungus disseminates to other areas • Sporothrix schenckii - a dimorphic fungus • fungus grow in soil and on plants and spores are inoculated into subcutaneous tissues by thorns and sharp needle of certain plants, like roses. • Diagnosis is based upon finding yeast cells in lymphatic fluid from lesions • In the laboratory at 25 C, characteristic colonies containing delicate branching hyphae with unique rosette conidia

5. Systemic Fungi - Systemic Mycoses • Histoplamosis - acute necrotizing, caseous granuloma of the lungs; in immunocompromised people or those exposed to high infectious dose, the yeast cells invade the mediastinal and hilar lymph nodes and disseminate via macrophages to the liver and spleen; in immunocompetent people the cellular immune response limits the spread of the yeast and confines the infection to mild flu-like symptoms; most primary infections are asymptomatic; has many features similar to tuberculosis • Histophasma capsulatum dimorphic fungus found in nature; mutiplies extensively in area where bird feces accumulate • Epidemiology - endemic geographical area; macroconidia(spores) are inhalated and taken into the lungs • Blastomycosis - chronic granulomatous ans suppurative disease of the lungs resulting in small areas of pulmonary consolidation; when confined to the lungs resolution results in scarring; dissemiation involves the skin, bones, • Blastomyces dermatiditis dimorphic fungus found in nature • Epidemiology broad geographic area with source unknown

6. Systemic Fungi - Systemic Mycoses • Coccidioidomycosis chronic, necrotizing mycotic infection of the lungs which pathologically resembles tuberculosis; begins as a bronchopneumonia with its inflammatory infiltrate; disseminates in immunocompromised people to many sites including skin, bones, meninges,liver, spleen.; symptoms range from asymptomatic to mild respiratory symptoms to diverse set of symptoms associated with the affected areas; another “great imitator” • Coccidioides immitis dimorhic fungus which grows in the soil of the S.W. United States; spores called arthrospores are inhaled into the alveoli and terminal bronchioles where they enlarge into “spherules”; spherules fill with endospores(yeast-like cells) which are released to form more spherules; • Epidemiology • Diagnosis

7. Systemic Fungi Systemic Mycoses • Cryptococcosis primary disease of the lungs with gramulomas and consolidation; readily spreads to the meninges and brain causing “meningoencephalitis” • Cryptococcus neoformans - only systemic fungus which is not dimorphic; its is a highly encapsulated yeast which accounts for its virulence • Epidemiology • Diagnosis

8. Opportunistic Fungi Mycoses • Candidia albicans • a common unicelluar fungus which is part of the flora of the oral cavity, vagina, and gastrointestinal tract; in this setting in becomes an opportunist especially in immunocompromised people • in culture, it grow as blastospores, pseudohyphae, and septate hyphae • candidiasis the collective term for infection involving Candida • cutaneous • vaginal • systemic • Aspergillus fumigatus/ A. flavus • Pneumocystis carnii