Common fungal traits:
- Many are dematiaceous, aka, pigmented fungi.
– It is thought that the melanin in their cells contributes to virulence. - Many are dimorphic, which means they exist in both hyphal and yeast forms.
- Reside in soil, on plants, and decaying vegetation.
- Trauma to the skin introduces pathogenic fungi to the underlying tissues.
– Thus, infections tend to occur on the extremities, especially the feet and hands, which are likely to be inoculated during gardening or field work. - Chronic, granulomatous lesions in the skin and deeper tissue.
– Often, histopathologic samples will show Splendore-Heoppliphenomenon, aka, asteroid bodies, which are characterized by eosinophilic materials radiating from the microorganisms. - Initial lesion occurs at the site of inoculation, for example, in the skin of the feet
– Then spreads to deeper tissues, which can include the lymphatics, muscles, and connective tissues. - Rarely disseminate to other organs.
- Long-term antifungals can be used to treat some subcutaneous mycoses.
Lymphocutaneous sporotrichosis
“Rose Gardener’s Disease”
– Many individuals are inoculated via rose thorns.
- The fungi most often responsible are members of the Sporothrix schenckii complex.
- Mycosis manifests as linear cutaneous nodules and ulcers that begin at the site of inoculation and travel along the path of the draining lymphatics.
– In some patients, the lesions will become suppurative; the discharged pus contains fungi that is useful for diagnostic purposes.
Chromoblastomycosis
Chromomycosis
- Caused by a variety of fungi
– Fonsecae, Cladosporium, Phialophora, etc. - Histopathologic samples show characteristic Medlar bodies (aka, sclerotic bodies or muriform cells).
– Medlar bodies are cells with transverse septa and thick, pigmented cell walls; some liken them to copper pennies.
In the sample, we can see some Medlar bodies within a giant cell. - Chromoblastomycosis produces slowly developing, chronic lesions that can cause progressive tissue fibrosis.
– Lesion morphology varies; for example, some patients have warty or “cauliflower-like” nodules, while others develop plaques with central scarring. - Mild cases where warty nodules are involved may be cured by excision.
- However, excision is not practical in patients with extensive lesions, as we see in the example of plaques; thus, long-term antifungals are the preferred treatment in such cases.
Eumycotic Mycetoma
Madura foot or Maduramycosis
- Caused by Madurella mycetomatis and other fungi.
- Because mycetoma is also caused by bacteria, it’s important to culture samples from the patient to rule out actinomycetemycetoma, which requires a different intervention.
- Eumycotic mycetoma is characterized by painless nodules that progress to ulcers; the ulcers discharge fluid and granules.
– Granules comprise the fungal hyphae
– The color of the granule is indicative of the microorganism type
M. mycetomatis granules are dark brownish-black. - Eumycotic mycetoma is a chronic and progressive condition,and new sinuses form as older sinuses heal.
- The draining sinuses produce swelling and tissue deformity;infection can ultimately invade and destroy deeper tissues.
- Unfortunately, eumycotic mycetoma often responds poorly to antifungal treatments, so amputation is often necessary to prevent further destruction.
Subcutaneous Entomophthoromycosis
Conidiobolus coronatus
- Conidiobolomycosis most commonly affects adults.
- Inhalation produces infection in the nasal and paranasal sinuses.
- Swelling and deformity of the nose and upper lip can be quite dramatic, though relatively painless.
Basidiobolus ranarum
- Basidiobolomycosis more commonly affects male children.
- Produces “rubbery” dark lesions on the buttocks, thighs, and shoulders.
– Gastrointestinal involvement is possible, though rare.
Subcutaneous Phaeohyphomycosis
- Various species
– Exophiala, Bipolaris, Curvalaria, etc. - Histopathologic samples are characterized by irregular hyphae.
- Infection produces slow growing cysts, or, sometimes, plaques.
