Subcutaneous Fungal Infections Flashcards
General overview
Mycoses of implantation
Fungi in natural environment directly inoculated into the dermis/subcut tissue through a penetrating injury
COMMON
Sporotrichosis
Mycetoma
Chromoblastomycosis
RARE
Phaeohyphomycosis
Lobomycosis
Rhinosporidiosis
IX FOR DX
Aspirate or swab of pus/exudate
Skin bx for tissue culture, both from edge and from centre of the lesion placed in sterile containers for immediate dispatch OR placed in sterile saline soaked gauze if cannot be processed immediately (delays in processing increases likelihood of bacteria/saprophytic fungi contaminating samples)
Skin bx for histo and special stains
- H&E —> if fungi is naturally pigmented
- Grocott-Gomori stain
- PAS
Sporotrichosis
Acute or chronic fungal infection
Sporothrix schenckii
Grows on decaying vegetable matter i.e. timber in mines, source probably the soil
Tropics and subtropics
CLINICAL FEATURES Cutaneous vs systemic 2 types of cutaneous sporotrichosis - Lympangitic form (most common) - Fixed form
Healthy ppl in cutaneous sporotrichosis
Lympangitic form
- Indurated and ulcerating nodules
- Exposed skin on upper extremity —> lympangitis sporotrichosis pattern
- Nodules/pustules forms —> breaks down into ulcer
- Chronic course if untreated —> chain of lymphatic nodules (sporotrichoid spread)
- New nodules appear at intervals of a few days —> soften —> ulcerate —> connected by tender lymphatic cords
- Thin purulent discharge from primary and earliest lesions
- Primary lesion may heal spontaneously
- Regional LN —> may break down
Fixed form
- Pathogen remaims localised at point of inoculation
- Varying morphology —> Acneiform, nodular, ulcerated, verrucous, infiltrated plaques, red scaly patches
- Verrucous may be extensive
DDX
Leishmaniasis
M. Marinum
RISK FACTORS Workers using straw as packing material Forestry workers Florists Gardeners Domestic cats in Brazil
PATHOGENESIS
Fungus introduced into skin or mucous membranes by trauma i.e. minor puncture wound caused by thorn or splinter, insect bite
Not contagious
May remain localised in subcut tissue, spread locally in subcut lymphatics, widely disseminated in bloodstream after pulmonary infection —> dependant on host immunity
CLINICAL VARIANTS
Systemic sporotrichosis (rare, immune impairment i.e. alcoholics, HIV)
Probably follows inhalation
Presents either with pulmonary disease vs focal or widely disseminated lesions in joints, meninges, skin
IX
Skin bx for histo and special stains
Skin bx for tissue culture MCS
HISTO
Mixed granulomatous reaction with neuts
Small cigar shaped or oval yeats, surrounded by thick radiate eosinophilic substance as a foreign body tissue reaction (asteroid bodies)
MX
Systemic antifungals
SYSTEMICS cutaneous form (first line)
Itraconazole 100-200mg daily until clinical recovery (at least 3 months)
Terbinafine 250mg daily until climical recovery (at least 3 months)
SYSTEMICS cutaneous form (second line)
KI saturated solution —> initial dpse 5 drops daily, increasingly slowly to 4-6mls TDS (continued for another 3-4 weeks after clinical cure)
SYSTEMICW systemic form (first line)
Amphotericin B
COURSE/PROGNOSIS
Cutaneous sporotrichosis not life threaatening
May resolve spontaneously or persist chronically if untreated
COMPLICATIONS
Disseminated skin sporotrichosis in HIV/AIDS
Chromoblastomycosis
Pigmented fungi
Several species -
- Phialophora verrucosa
- Fonsacea pedrosoi
Wood, soil
Tropics
CLINICAL FEATURES
Slow growing exophytic lesions —> develops over years
Exposed sites
Usually feet and legs
Sometimes Arms, face, neck
Warty papules slowly enlarges —> hypertrophic plaque —> central scarring
May present as an ulcer or be assoc with secomdary ulceration
Usually painless
If infected —> secomdary itch, pain
Scratching —> satellite lesions
+/- lymphatic spread (sporotrichoid spread)
RISK FACTORS
Agricultural workers
PATHOGENESIS
Infection usually results from trauma i.e. puncture from wood splinter
DDX Blastomycosis Cutaneous TB Leishmaniasis Syphilis Yaws
CLINICAL VARIANTS
Psoriasiform lesions
Haematogenous spread
Brain abscess
IX
Skin bx for histo and special stains (H&E, Grocott silver, PAS)
Skin bx for culture MCS
HISTO
Foreign body granuloma
Isolated areas of microabscess formation
Chestnut, golden brown deeply pigmented groups of fungal cells within granuloma/giant cells “ sclerotic cells” “copper pennies”
MX Systemic antifungals (first line)
Heat Rx (second line)
- Local application of heat daily with a heat-retaining gel pack at a warm and comfortable temp
- shrinkage of lesions usually takes 2-3 months
LN2 (second line)
Surgical excision (third line)
- Very small lesions, but needs to be combined with systemic antifungals
- Excision of large plaques risk decelopment of satellite lesions around excision site
SYSTEMICS (first line)
Itraconazole 100-200mg daily until clinical recovery
Terbinafine 250mgdaily until clinical recovery
COURSE/PROGNOSIS
Chronic
Non fatal
COMPLICATIONS
Secondary infection —> lymphatic stasis —> elephantiasis
SCCs within chronic lesions
Phaeohyphomycosis
Localised subcut or intramuscular infection
A range of brown pigmented fungi
Species -
Exophiala jeanselmei
Exophiala dermatitidis
Phialophora sp.
Tropics
CLINICAL FEATURES
Well defined single Cyst, abscess
Trunk, limbs
Not painful
RISK FACTORS
Immunosuppression mainly to steroids
PATHOGENESIS
Traumatic implantation of environmental fungi
DDX
Baker cyst
Large Pilar cyst
IX
Skin bx for histo and special stains (H&E, Grocott silver, PAS)
Skin bx for culture MCS —> identification may require special lab d/t many species involved
HISTO
Pigmented Fungi within Subcut inflammatory cyst
Well organised wall with surrounding fibrosis, mixed cellular infiltrate, multinucleate giant cells, lymphocytes, macrophages, neuts
MX
Excision + itraconazole post surgery
COURSE/PROGNOSIS
Does not heal spontaneously
Not fatal
Mycetoma
@
Madura foot
Characterised by formation of grains within abscesses
Grains discharged to the surface through draining sinuses
Not contagious
Various species of fungi (eumycetoma) and actinomycetes (actinomycetoma)
CAUSES
Dark grain fungi (brown grains)
- Madurella mycetomatis***
- Madurella grisea
Pale grain fungi (white or yellow grains)
- Scedosporium apiospermum***
- Fusarium spp.
Actinomycetes (red grains)
- Streptomyces somaliensis
- Nocardia brasiliensis and others
- Actinomadura madurae
Soil, plants
Tropics, subtropics
CLINICAL FEATURES
Foot, lower leg
But may be anywhere on body
Early stage —> Firm painless nodules
Subsequently —> papules, pustules break down to form draining sinuses that appear on the skin surface
Area hard and swollen
Without significant pain
Extension to deeper structures bone, joints —> periostitis, osteomyelitis, arthritis
Advanced cases —> destruction of bine within infected area may be almost complete —> gross deformity
Usually multiple sinus tracts draining pus —> may remain open for months, may close and reopen, may be replaced by new sinuses
Discharge may be purulent or seropurulent
End result of gross swelling with serious deformity
RISK FACTORS
Agricultural workers
PATHOGENESIS
Implanted subcut usually after penetrating injury
DDX
Chronic osteomyelitis d/t bacteria, TB
CLINICAL VARIANTS
lymph node
Isolated bone involvement
IX
Incise pustules and swab Pus sent for histology/direct microscopy under KOH
Pus for MCS
MRI to assess extent of deep destruction
HISTO
Chronic inflammatory reaction —> focal neut abscess, scattered giant cells, fibrosis
White, yellow, red, black grains/granules in the centre of the inflammatory response
Grains may be discharged in pus through multiple sinuses to skin surface
Invades muscles, bones
MX
If localised and small and can be excised without residual disability —> surgery
Otherwise systemic Rx
SYSTEMICS (actinomycetes, first line)
Dapsone/co-trimoxazole + Streptomycin
Dapsone/co-trimoxazole + Rifampicin
SYSTEMICS (fungi, first line) Ketoconazole Griseofulvin Terbinafine Voriconazole Itraconazole
SURGERY (last resort)
Radical surgery i.e. amputation ought to be considered carefully —> however may he the inly means of removing infection in some cases
COURSE/PROGNOSIS Progression inevitable, but slow No spontaneous remission Deformity, reduced mobility May be fatal
COMPLICATIONS
Bone destruction —> deformity, osteomyelitis
Scalp —> deep extension leads to skull penetration
Chest wall —> lung invasion
Lobomycosis
Rare
Lacazia loboi (never been isolated in culture)
CLINICAL FEATURES Keloidal skin lesions Well localised Anywhere on the body, but usually on exposed sites Legs, arms, face Assoc with injuries to skin Autoinoculation followimg injury —> spread from ome site to another No marked lymphangitis No visceral dissemination
PATHOGENESIS
Assoc with water, entry into wounds
DDX
Chromoblastomycosis (clinical resemblance)
IX
Skin bx for histo and special stains —> microscopic exam establishes dx
Fungus never isolated in culture
HISTO
Diffsue infiltrate of lymphocytes, macrophages, giant cells containing fungal cells
Special stains —> oval, round fungal cells align/join by short tubular structures into short chains
MX
Surgical excision
No medical Rx
COURSE/PROGNOSIS
Remains localised
Slowly expands over years if untreated
COMPLICATIONS
SCC in chronic lesions
