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.