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Subcutaneous mycoses


1. Mycetoma

Chronic granulomatous infection of the exposed part of the body

  1. First observed in Madurai district of South India (1842)
  2. Infection follows traumatic inoculation of the organism into the subcutaneous tissue
  3. Triad of symptoms: tumefaction of involved tissue + draining sinus tracts + grains or sulphur granules (microcolonies of fungi) 

a. Three types:

  1. Eumycetoma (more prevalent in north India)
  2. Actinomycetoma (more prevalent in south India)
  3. Botryomycosis


Colour of Grains



Madurella mycetomatis


Madurella grisea


Exophiala jeanselmei


Acremonium kiliense


Pseudallescheria boydii




Actinomadura madurae

White, Yellow

Actinomadura pellitieri


Nocardia asteroids


Nocardia brasiliensis


Streptomyces somaliensis




Staphylococcus aureus


Escherichia coli


Pseudomonas aeruginosa



b. Laboratory diagnosis:

  1. Direct microscopic examination: Grains are mounted in a drop of 10% KOH on a slide and crushed under coverslip. In actinomycetoma, the grains are composed of thin filaments (1μm diameter) while in eumycetoma there are broad hyphae (2-6μm diameter).
  2. Culture: for definitive diagnosis

c. Treatment:

  1. Actinomycetoma responds to sulphonamides and other antibiotics
  2. Eumycetomas are resistant and may require amputation 

2. Chromoblastomycosis

  1. Chronic localized infection of the skin and subcutaneous tissue
  2. Irregular, rough, cauliflower-like lesions involving mostly lower legs & feet
  3. Caused by following dematiaceous fungi:
  • Phialophora verrucosa
  • Fonsecaea pedrosoi, F. compacta
  • Cladosporium carrionii
  • Rhinocladiella aquaspersa
4. Infection follows traumatic inoculation of the organism into the subcutaneous tissue
5. Microscopy of biopsy shows: thick welled brown cells divided by transverse septa called SCLEROTIC bodies/ copper penny/ muriform cells/ medlar bodies


3. Phaeohyphomycosis

  1. The fungus in the tissue is present in the form of darkly pigmented septate hyphae and not as thick walled cluster of cells
  2. Caused by exogenous dematiaceous fungi which normally occur in the nature
  3. Commonly implicated fungi: Wangiella dermatitidis, Exophiala jeanselmei, Xylophypha bantiana 

4. Chromomycosis

  1. Term chromomycosis includes chromoblastomycosis and a variety of diseases by other dematiaceous fungi, like phaeohyphomycosis of subcutaneous tissue, CNS, paranasal sinuses 

5. Rhinosporidiosis-

  1. Caused by Rhinosporidium seeberi
    1. Chronic granulomatous disease characterised by friable sessile or pedunculated polyps or wart like lesions
    2. Nasal (commonest), occular, cutaneous, other mucocutaneous sites
    3. 90% cases have been reported from Srilanka, India, South America
    4. India: Tamil nadu, Kerala, Orissa, Andhra Pradesh
    5. The causative organism has not been cultured
    6. Very little known about its mode of transmission. Probably transmitted by dust or water
    7. Infection is common in Persons bathing in stagnant pools of water and paddy cultivators 

b. Laboratory diagnosis:


  1. Biopsy stained with H&E, GMS, PAS, Carminophilic (mayer’s muciarmine stains inner layer of sporangium & outer layer of endospore)-Sporangia (350μm in diameter) filled with endospores (6-9μm in diameter) 

6. Sporotrichosis

  1. Chronic pyogenic granulomatous infection of the skin & subcutaneous tissue
  2. Caused by dimorphic fungus Sporothrix schenkii
  3. Fungus is found in soil, decaying wood, thorns
  4. Infection seen in rural workers, gardeners, florists, carpenters
  5. India: prevalent in sub-Himalayan areas from Himachal Pradesh to Assam
  6. Infection is due to implantation of spores through injured skin 

a. Clinical forms:

  1. Lymphocutaneous (commonest type)
  2. Fixed cutaneous/Mucocutaneous/Disseminated/Pulmonary
    The initial lesion is a small ulcerated nodule on the arm or forehand. Nodules and abscesses occur along the draining lymphatics and the regional lymphnodes enlarge and ulcerate. The primary lesion may remain localized or disseminate 

b. Laboratory diagnosis:

  1. Direct microscopic examination: PAS, methenamine silver or fluorescent staining shows oval, cigar shaped yeast cells. Splendore-Hoeppli or Asteroid phenomenon: central basophilic yeast cell with eosinophilic (immune complex deposition) material radiating from it
  2. Culture: Growth on SDA at 25°C shows delicate hyphae bearing pyriform conidia arising directly from hypha or developing in a rosette pattern at the ends of conidiophore
  3. Yeast conversion: brain heart infusion blood agar at 37°C to show dimorphism

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