Subcutaneous Mycoses

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Usually the result of traumatic implantation of fungus into skin.  Lesion develops at the site of the lesion.

  1. Mycetoma (clincal syndrome of localized, indolent, deforming, swollen lesions and sinuses, involving cutaneous and subcutaneous tissues, fascia, and bone; usually occurring on the foot or hand) - etiologic agent may be bacterial or fungi.  Discussion here will be restricted to fungal mycetoma.
  2. Chromoblastomycosis (subcutaneous and cutaneous tissues of the hands and feet).
  3. Phaeohyphomycosis (face, cornea of eye, subcutaneous and cutaneous part of skin, occasionally cerebral and systemic)
  4. Sporotrichosis (cutaneous and subcutaneous tissues and adjacent lymphatics that suppurate, ulcerate and drain)
  5. Lobomycosis (subcutaneous and cut. tissues over different parts of body).
  6. Rhinosporidiosis (nasal cavities, mucocutaneous tissue - rarely it does effect the vagina, penis, anus, ears, and throat region)

Mycetoma - clincal syndrome of localized, indolent, deforming, swollen lesions and sinuses, involving cutaneous and subcutaneous tissues, fascia, and bone; usually occurring on the foot or hand) - etiologic agent may be bacteria or fungi.
  • one potential causal agent can be Pseudallescheria boydii, a soil/water inhabiting fungus with worldwide distribution.  However other fungi can be involved.
  • fungi associated with fungal mycetoma are opportunistic
  • mycotic mycetoma - usually more common in men (3:1 to 5:1) than in women
  • usually results from trauma or puncture wounds to feet, legs, arms and hands (usually on the feet)
  • starts out as tumor-like to subcutaneous swelling
  • ruptures near the surface; infects deeper tissues including subcutaneous tissues and ligaments (tendons, muscles and bone are usually spared)
  • small particles or grains leak out of the lesions -  these represent the to yellowish microcolonies
  • lesions of mycetoma seldom heal spontaneously
  • disease is chronic may continue for 40-50 years
  • P. boydii is resistant to all systemically useful drugs, including amphotericin B, KI, 5-fluorocytosine, 2-hydroxystilbamidine
  • ketoconazole appears to be ineffective in clinical trials
  • intravenous miconazole (9 mg per Kg of body weight sometimes higher doses) shows promise
  • surgery and removal of tumor ( if small it is encapsulate, if larger amputation my be required)
  • Combining miconazole and surgery may prove useful in effectively treating the disease.

Chromoblastomycosis -  chromomycosis or verrucous dermatitis.
  • Disease is one of hyperplasia, characterized by the formation of verrucoid (rough), warty, cutaneous nodules, which may be raised 1-3 cm above the skin surface.  The roughened, irregular, pedunculated vegetations often resembles the florets of cauliflower
  • This disease is caused by Fonsecaea pedrosoi and Phialophora verrucosa (identical to Cadophora americana which causes bluing of lumber), both of which are dematiaceous fungi (darkly pigmented)
  • occurs rarely in animals (such as, horses, cats, dogs, and frogs)
  • soil-inhabiting fungi
  • susceptibility enhanced by going barefoot or wearing sandals
  • found almost exclusively in laborers
  • enters hand or feet after trauma
  • found primarily in the tropics or subtropics
  • dull red or violet color on skin may resemble a ringworm lesion
  • develops into a verrucous lesion
  • pruritus (itchiness) and papules may develop
  • fungus gets under the skin (produces bumps)
  • bumps may block lymphatic system and cause elephantiasis
  • sometimes bacterial infection may enter and cause a secondary infection
  • rarely this fungus spreads to other areas of the subcutaneous tissue.
  • potentially may spread to brain (life-threatening in that case)
Identification
  • biopsy tissue - look at the skin for fungus
  • hematoxylin stain - look for fungal cells scattered among skin cells
  • attempt to culture fungus from biopsy tissue must always take place to identify the etiological or causal agent
  • colonies of fungi are dark or blackish
  • Two species implicated in this mycosis - each may produce several spore types
    • Fonsecaea pedrosoi - Cladosporium type and Rhinocladiella type of conidiation
    • Phialalophora verrucosa - Phialophora type (flowers in the vase conidiation)
  • fungi found growing on plant debris, wood, soil.
Treatment
  • usually not fatal or necessarily painful
  • unsightly disease
  • no really good cure
  • thiabendazole - shows promise (given orally and on skin mixed with dimethyl sulfoxide [DMSO] - to deliver drug) - experimental drug
  • surgical excision, electrodesiccation, or cryosurgery are useful in early stages of disease
  • application of heat to infect site has been reported to effect a cure of the disease after six months of treatment (using pocket warmers)
  • itraconazole shows promise in clinical trials.

Phaeohyphomycosis
  • amalgam of clinical diseases caused by a wide variety of dematiaceous fungi
  • characterized by the presence of brown pigmented fungal elements in host tissue
  • etiologic agent varies, and can be represented by a number of different fungal species
  • infections may vary from being superficial and contained in the stratum corneum of the skin, to cutaneous and subcutaneous.
  • in rare instances infections may become invasive systemic (invading various organs) and/or  cerebral
  • in diagnosis, materials from cysts, nodules, abscesses and other infected tissues may be examined under the microscope directly with 10% KOH.  The fungi are usually pigmented dark brown to hyaline
  • if possible, material can be subcultured onto a selective isolation medium, for several weeks at room temperature;  identification of genus and species is made, based on morphological and cultural characteristics
  • the name, "Phaeohyphomycosis" is not meant to supplant established clinical names of diseases, particularly when the etiological agent is known
  • treatment usually involves surgical excision of fungus and treatment of with antifungal drugs (amphotericin B, 5-fluorocytosine, ketoconazole, or another imidazole).

Sporotrichosis (Gardener's disease)
  • Sporotrichosis is most commonly a chronic infection characterized by nodular lesions of the cutaneous or subcutaneous tissues and adjacent lymphatics that suppurate, ulcerate, and drain
  • the etiologic agent, is Sporothrix schenckii
  • the fungus is found distributed throughout the world
  • the fungus gains entrance into the body through traumatic implantation into the skin or rarely, by inhalation into the lungs.
  • first case presented with the clinical picture of sporotrichosis was recorded by Schenck in 1898 from Johns Hopkins Hospital in Baltimore
  • Epidemics of sporotrichoisis have been reported from time to time.
  • In South Africa, over the space of two years, almost 3000 cases occurred involving miners who brushed against timbers of a mine shaft on which the fungus was growing.  The epidemic was terminated by treating the timbers with a fungicide.
  • An epidemic occurred among brickyard workers who, after the drinking much beer, began tossing bricks at each other, causing many skin abrasions.
  • The disease may be found in other animals, including horses.
  • The fungus gains entry into the body through some trauma to the skin.
  • The fungus is a saprophyte on plant debris
  • scratches from thorns or splinters, cuts while handling potting soil, sphagnum moss, or grasses allow the fungus to gain entrance into the body
  • This diseases has also occurred following cat scratches, parrot bites, dog bites, insect stings, injury by metal particles, handling fish, hammer blows, etc.
  • occupational hazard of greenhouse workers and rose growers
  • Lymphocutaneous sporotrichoisis comprises up to 75% of all cases in most literature surveys.
    • first sins of infect may appear as soon as five days later
    • the average incubation time is three weeks.
    • The first sign of disease is the appearance of a small, hard, movable nontender and nonattached subcutaneous nodule. as the disease progresses in may become chronic, the lymphatics that drain the area of the initial lesion are involved
  • Fixed cutaneous sporotrichoisis
    • lesions manifest themselves as ulcerative, verrucous, infiltrated, or erythematoid plaques, or as scaly patchy, macular, or papular rashes that to not involve local lymphatics and remain "fixed"
  • Mucocutaneous, extracutaneous, disseminated and pulmonary sporotrichoisis do occur but these are relatively rare.
  • potassium iodide (KI) administered in milk is the drug of choice
  • immersion of infected regions in hot water and battery-operated "pocket warmers" have been utilized to bring about resolution of the disease
  • amphotericin B is the most effective drug used for the treatment of relapsed lymphocutaneous sporotrichosis and pulmonary and disseminated disease.
  • Fungus is diphasic, and will convert from a filamentous phase to a yeast phase when grown at a higher temperature (37C).
    Filamentous phase is hyaline, and produces delicate conidiophores and conidia.  Yeast phase is relatively nondescript, but budding yeast often irregularily-shaped to broadly elliptical (cigar bodies).

Lobomycosis or Lobo disease - etiological agent is Loboa loboi (yeast-like organism that has never been cultured)
  • Disease is chronic, localized, subepidermal infection characterized by the presence of keloidal, verrucoid, nodular lesions or sometimes by vegetating crusty plaques and tumors.
  • despite the name, the disease does not refer to an infection spread by wolves, or in any ways is it wolf-like.
  • disease first describe in patient known as Jorge Lobo (1931)
  • found in humans and dolphins.
  • many cells are found in skin tissue
  • chains of yeast cells form in tissue
  • keloids are formed (mass of hyperplastic, fibrous, connective tissue, usually at the site of a scar)
  • disease resembles blastomycosis or paracoccidiomycosis
  • cells are hyaline (not pigmented)
  • common in Amazon natives or rarely in northern South American or Central American people off the coast of Florida are found dolphins, have lesions which resemble LOBO.
  • what can be done? Not much, except perhaps surgery.

Rhinosporidiosis
  • infection of mucocutaneous tissue caused by Rhinosporidium seeberi
  • fungus has never been cultured, although current evidence suggests that it is a lower aquatic fungus - a "chytrid"
  • In arid countries most infections are ocular, and dust is postulated to ba vector
  • disease has been recorded in primarily in India, Ceylon, the Middle East, but also in South America, the U. S., and in almost every other country of the world.
  • age of patients varies from 3-90 some years, most patients are between 20 and 40 years of age when diagnosed
  • males account for 70-90% of cases, although this varies depending on age, site of infection, and geographic location.
  • eye infections seem to be more common in women
  • nasal, ocular, and other mucocutaneous regions may show signs of disease manifested as polyps and tumors
  • Treatment involves surgical remove of affected tissue
  • local injection of amphotericin B may be used as an adjunct to surgery to prevent reinfection and spread, although no studies have substantiated it's effectiveness
  • In tissue, the fungus produces spherules that possess a thick wall;  endospores are contained within.

This web page is organized and maintained by M. Huss.  Last updated 8-06-08.