Andrews Flashcards
Meaning of Mycosis?
A mycosis (plural: mycoses) is a fungal infection of animals, including humans.[1]
Mycoses are common and a variety of environmental and physiological conditions can contribute to the development of fungal diseases. Inhalation of fungal spores or localized colonization of the skin may initiate persistent infections; therefore, mycoses often start in the lungs or on the skin
Describe mold
Mold is the environmental form of fungi and is comprised of multicellular filaments called hyphae. Multiple hyphae collectively are called mycelium and at the ends are conidia, asexual spores formed by differentiation. This is the portion of mold that is inhaled and causes pulmonary disease. At room temp they form rough colonies when cultured.
Describe yeast
Yeast is the tissue form of fungi and is its unicellular form. Its reproduction is asexual via spores through asymmetric budding. The formation of spores allows for dissemination and survival in a hostile environment. At body temp they form smooth colonies that can appear slimy or mucoid.
Define Hyphae
Long branching filamentous structures of fungus. The main mode of vegetative growth and collectively called mycelium
Define Conidium
Asexually produced fungal spores that are the source of dispersal, located at the ends of the hyphae
Define sporangium
Sporangium (pl – sporangia) = Single or many celled balloon-like structure in which spores are produced
Define hyaline and dematiaceous
Hyaline = colorless fungi Dematiaceous = brown to black fungi
Causative organism for Basidiobolomycosis?
Basidiobolus ranarum
Findings seen in Basidiobololmycosis?
enviromental saprophyte, found in tropics
forms plainless, indurated subq nodule or swelling on thigh/butt
What is Conidiobolus coronatus?
similar to basidiobolomycosis (related organism)
affects face
What is Protothecosis
not a true fungus
- Prototheca wickerhamii
- often seen with exposure to contaminated water
- Solitary cutaneous plaques (sometimes eczematous), nodules or ulcers, as well as olecranon bursitis
Difficult to treat
Surgical excision and systemic antifungals (e.g. amphotericin B) are more effective in immunocompetent hosts
Organism in sporotrichosis?
Sporothrix schenckii
3 types of sporotrichosis?
Lymphocutaneous (regional lymphangitic)- naïve hosts
Fixed cutaneous- if prior exposure
Disseminated or pulmonary- immunocompromised host
Findings on culture of sporotrichosis?
Grows on Sabouraud dextrose agar (SDA)
25C: Rapidly shows a white colony, wrinkled and folded, tan to black over time
37C: Slow growing, whitish, pasty yeast like colonies and cigar shaped budding yeasts
Findings on biopsy of sporotrichosis?
Palisading granulomatous dermatitis surrounding a stellate suppurative abscess
Asteroid bodies – esosinophilic material around central yeast cell
PAS +, “cigar bodies” -round yeast cells (difficult to identify) – staining with fluorescent labeled antibodies may aid in recognition
Tx of sporotrichosis?
- topicals not effective
- Potassium Iodine
- Itraconazole
What is the Wolff-Chaikoff effect?
the effect when increasing doses of exogenous iodide inhibit thyroid hormone production leading to hypothyroidism
Differential for sporotrichoid lesions?
Mnemonic “SLANT” Sporotrichosis, S. aureus, S. pyogenes, S. boydii Leishmaniasis Atypical mycobacteria (m. marinum) Nocardiosis Tularemia, Toxoplasmosis, Tuberculosis
Glanders (burkholderia mallei) Dimorphic and opportunistic fungi Opportunistic fungi in IC hosts (fusarium, alternaria spp) Cat scratch disease Anthrax and Cowpox Acanthamoeba spp.
What are the three different types of mycetoma (fungal tumors)?
It is a granulomatous infection of dermal and subcutaneous tissue that may extend to muscle or even bone and is due to implantation. Mycetoma is differentiated from other mycoses by its characteristic draining sinuses containing grains (sclerotia, sulfur granules) and local edema.
- Actinomycetoma - filamentous aerobic and anaerobic bacteria i.e. Nocardia brasiliensis, Actinomadura madurae
More common 3:1 - Eumycetoma - true fungi
- Botryomycosis - true bacteria, s. aureus, pseudomonas
Where are on the body do mycetomas infect?
Granulomatous infection of dermis and subcutaneous
Differs from other mycoses – slowly progressive, chronic, subcutaneous infection, swelling with draining sinuses (sulfur granules) (sclerotia)
Instep of the foot, painless, firm nodule with tissue destruction
May involve the underlying fascia and bone
Enter by traumatic/penetrating inoculation, (MC on foot)
Toe webs, hands, arms, chest, jaw, buttocks
Unexposed sites are almost always actinomycetomas
What is the course of infection with mycetomas?
Foot is m.c. site of infection
Followed by the hand, trunk and scalp
Typically unilateral and begins as a painless papule
Once SubQ tissues infected -> surrounding soft tissue swells and starts to form purulent draining sinuses
Drainage contains the characteristic grains (sclerotia)
Represent compact masses of fungal colonies
Vary in size from minute to almost a centimeter in diameter
Invasion of deeper tissues then ensues -> sometimes cavities are formed within involved bone
Generally asymptomatic!!
What is seen on biopsy and culture of actinomycetomas?
Culture
Brain-heart infusion agar and sabouraud dextrose agar, 0.5% yeast extract
Biopsy
Thin branching gram + filaments 1-2 micrometers thick
H + E: PEH and suppurative and granulomatous inflammation with stellate abscesses containing grains (asteroid bodies)
Stain well with Giemsa, Brown-Brennen
What is seen on biopsy and culture of eumycetoma?
Culture
Sabouraud dextrose agar, 0.5% yeast extract (hyphae and chlamydoconidia)
Biopsy
Thick filamentous hyphae 2-5 micrometers thick
Stain well with PAS, Gomori methenamine silver
What are the treatments for eumycetoma and actinmycetomas?
Actinomycetoma
Responds to antibiotics
Bactrim, sulfadiazine, sulfones, dapsone
A. israelii: PCN in large doses is curative
N. asteroides & N. brasiliensis: Sulfonamides
Rifampin & co-trimoxazole have been used
Severe refractory cases may need impenem
Eumycetoma
Early, surgical removal of area, amputation necessary in severe cases
+ Antifungal treatment (itraconazole, fluconazole, posaconazole)
Relapses are common
What are the three characteristics that make up a mycetoma?
Tumefaction (edema)
Sinus tracts
Granules (expelled organisms)
What are the causes of chromoblastomycosis?
Caused by one of 6 dematiaceous fungi: (melanin)
“Fond of Pedro’s Compact Monochromatic Car”
“Fun with PCR”
Fonsecaea pedrosoi (most common, 90%)
Fonsecaea compacta
Fonsecaea monophora
Phialophora verrucosa
Cladophialophora carrionii
Rhinocladiella aquaspera
(isolated cases) Exophiala spinifera & jeanselmei
What does chromoblastomycosis look like clinically?
Starts as small papule or warty growth Foot or lower leg
Typically unilateral
Verrucous (cauliflower-like lesions) (TH2 immunological response!)
Granulomatous plaque, annular with central atrophy, scarring (TH1 imunological response)
Direct extension spread and satellite lesions
Regional lymphadenopathy (2° bacterial infection)
Usually no constitutional symptoms
Rarely – Squamous cell carcinoma develops in long standing lesions
How is chromoblastomycosis diagnosed?
Histology
PEH, intraepidermal abscess, granulomatous inflammation
Pigmented fungal sclerotic bodies (Medlar bodies “copper pennies”), often seen with embedded splinter and are pathognomonic
Brown, round thick walled cells
Culture
Black, velvety, heaped up colonies (all produce melanin)
- Pseudoepitheliomatous hyperplasia, intraepidermal abscesses, and suppurative and granulomatous inflammation within the dermis are the typical histologic findings. Round, pigmented bodies, which are said to resemble “copper pennies” (6 to 12 microns), are present in the dermis, both extracellularly and within giant cells. These are unique to chromoblastomycosis and are also known as “Medlar bodies” or sclerotic bodies[2
What fungus causes lobomycosis?
Locazia loboi
Describe clinical manifestation of lobomycosis.
Chronic fungal infection characterized by cutaneous nodules that resemble keloids. May involve regional lymph nodes.
What will the biopsy show for lobomycosis?
Biopsy
Atrophic epidermis
Thick walled refractile spherules, only one or two buds
Cellular granulomatous infiltrate: PEH, histiocytes, giant cells, lymphocytes; atrophy
Can not be cultured normally
Can grow on mouse footpads
What is the treatment of lobomycosis?
Recurrence is common!
Surgical excision, cryotherapy
Antifungals often ineffective
Itraconazole 100mg/day and Clofazamine 100mg/day some benefit
What organism causes Rhinosporidiosis?
Rhinosporidium seeberi
What are the clinical manifestations of Rhinosporidiosis?
Polypoid disease involving mucosal surfaces
Nasal mucosa, conjunctival, oral, genital (condylomata)
Small papillomas develop into large polyps, pedunculated tumors with fissured warty surface
Grayish white flecks on tissue (transepithelial elimination of large sporangia)
Conjunctival – small, pinkish papillary nodules that enlarge, darken, and become lobulated
What is the treatment of Rhinosporidiosis?
Excision or electrosurgery is most common
Antifungals little help
May try cipro (works against M. aeruginosa)
What will biopsy show of Rhinosporidiosis?
Diagnosis: Biopsy (histology) – organism does NOT grow in culture
Spherules (7-10μm) in large cystic sporangia (300μm)
Endospores are rough like raspberries
Granulomatous response 50%
Transepithelial elimination is common
What are the 3 forms of infection with Coccidiomycosis?
Primary pulmonary
Inhalation of dust laden with arthroconidia
Disseminated (coccidiodal granuloma)
<1% of infections
Immunosuppression increases risk of dissemination
Skin lesions in 15-20% of disseminated cases
Primary Cutaneous
Rare
What are the clinical manifestations of primary pulmonary infection with coccdiomycosis?
Primary pulmonary infection:
60% infected are asymptomatic
Mild respiratory infection, low grade fever, flu-like sx
Incubation 10 days - weeks
Fever, pleuritic CP, HA, resp distress, anorexia, malaise, myalgias
Large % develop CXR findings
Initial morbilliform eruption may appear
Within weeks may develop allergic skin manifestations
Erythema nodosum
Erythema multiforme
Most recover spontaneously
What are the findings on histology for coccdiomycosis?
Diagnosis:
CXR
KOH
Biopsy
Spherules, unencapsulated, thick refractile wall and granular interior, average 20μm
Stain well with PAS, GMS and H&E
Culture
Highly infectious (only in labs with hoods!!)
SDA Dimorphous, seen at both temperatures
Fluffy white-tan colony
Mycelia have 90° branching and septated hyphae
Spherical bodies, many thick-walled barrel-shaped
What are the skin findings of coccdiomycosis?
Cutaneous Patterns Toxic erythema (pulmonary) Diffuse morbilliform eruption early in disease Hypersensitivity reaction (pulmonary) Erythema nodosum Erythema multiforme Primary cutaneous Nodules that ulcerate
Secondary cutaneous (disseminated)
Papules, pustules, abscesses, granulomatous plaques (may look like molluscum in HIV patients)
Often on central face, NL folds
What is the DDx of parasitized macrophages?
His GRL Pen
Histoplasmosis- H.capsulatum
Penicilliosis- P. marneffei
Granuloma inguinale- Calymmatobacterium granulomatis
Rhinoscleroma- Klebsiella rhinoscleromatis
Leishmaniasis- Leishmania spp
How do we diagnose Histoplasmosis?
Diagnosis
Biopsy
2-3μm round bodies within cytoplasm of macrophages
Single or budding with thin isthmus between buds
Pseudocapsule (artifact), halo (rim of clearing) around organism
African: 10-13μm organisms within multinuclear giant cells
Organisms stain with Giemsa, PAS or GMS
Cultures
Blood, sputum, bronchial washings, spinal fluid, lymph node smears, ulcers
SDA, Mycosel, brain-heart infusion (blood added)
25C: Fluffy white, turns tan, septate hyphae, pear-shaped microconidia, thick-walled echinulate macroconidia
37°C: moist yeast colony, small, round-oval budding cells
Immunology
Best test is urinary ELISA
Histoplasmin skin test, complement fixation test > 1:32 = active or recent infection
Culture remains the gold standard
DDx Pseudoepitheliomatous Hyperplasia?
Atypical mycobacterium Actinomycosis Blastomycosis Paracoccidiosis Coccidioidomycosis Chromomycosis Protothecosis Sporotrichosis Halogenoderma
Differential for Molluscum-like lesions
“CCHIP”
Cryptococcosis
Coccidioidiomycosis
Histoplasmosis
Penicillium
