Subcutaneous mycosis Introduction: The term subcutaneous mycosis means a disease in which the pathogen, an exosaprophyte, penetrates the dermis or even deeper during or after a skin trauma. The lesions gradually spread locally without dissemination to deep organs. However, most fungi which cause subcutaneous mycoses can also occasion deep mycoses in patients with severe underlying abnormalities (via the respiratory tract). Subcutaneous mycoses occur exclusively or predominantly in the tropics.

Local Primary infection of subcutaneous Leukocytosis or eosinophilic response Leading to cysts formation or granuloma Mostly chronic May confuse with secondary skin infection due to systemic fungi There are four general types of subcutaneous mycoses: chromoblastomycosis, mycetoma, Rhinosporidiosis, and sporotrichosis. All appear to be caused by traumatic inoculation of the etiological fungi into the subcutaneous tissue.

Types of Subcutaneous Mycosis: Mycetoma Rhinosporidiosis Sporotrichosis Chromoblastomycosis

FUNGI THAT CAUSE CHROMOMYCOSIS. (Chromoblastomycosis) Clinical presentation Chronic watery localized infection of cutaneous and subcutaneous tissues characterised by vegetative lesions, which occur predominantly on the lower limbs but other parts of the body may also be affected. The term MOSSY FOOT is sometimes used when the foot is affected. Characterized by localized, slowly expanding verrucous lesions Lesions painless, but itching.

Pathogens: The pathogens are dark-walled fungi which are saprophytes on plants and wood. Caused by different dematiaceous fungi Fonsecaea compacta Fonsecaea pedrosi Cladophialophora carrionii Phialophora verucosa Phialophora dermatitidis

Laboratory diagnosis. Sample: Skin scrapings, crusts and/or tissue biopsy All theses species are monomorphic moulds that produce dark-colored hyphae. Direct microscopy: 10% KOH  The different species of fungi that cause chromomycosis have a similar appearance in a direct KOH preparation.  In crusts and skin scales, long µ m large dark coloured, branching, transverse septate hyphae 'sclerotic cells measuring 2-5 µ m in width can be seen.  Thick walled brown cells measuring 5-15 µ m can sometimes be seen in exudates from skin lesions

Culture: Culture on SDA and BHIA (4-6 weeks) Using the following techniques: H&E, PAS, and Silver stain This is necessary to identify the different species. Identification is based on the type of conidiophore produces. Most species are slow- growing. Skin scales and crusts are best transferred in paper packages as shown before and skin biopsies should be fixed and send in formal saline fixative.

Serology: There are no commercially available serological tests to diagnose choromomycosis. Precipitant tests using double diffusion techniques and counterimmunoelectrophoresis are used in some reference laboratories. Management Difficult Antifungal but many clinicians find chromomycosis very resistant to antifungal treatment. Surgery if possible (ideal for early lesions)

Chromoblastomycosis (summary) Chronic cutaneous and subcutaneous Caused by group of dematiaceous fungi Characteristic direct morphology Culture for identification Surgery and antifungal agents