• Systemic granulomatous disease caused by a
dimorphic fungus, Histoplasma capsulatum.
• Species name is misnomer as it is not
• Also known as Darling's disease (because they
was first reported by Samuel Darling in1905 )
4. HISTOPLASMOSIS- Pathogenesis
• Transmitted by- inhalation of spores (i.e.
microconidia) which usually circulate in the air
after the contaminated soil is disturbed.
• Spores enter into the lungs engulfed
inside the alveolar macrophages
transform into yeast forms .
• Yeasts survive within the phagolysosome of
the macrophage by producing alkaline
substances (bicarbonate and ammonia).
5. HISTOPLASMOSIS- Clinical Manifestations
• Pulmonary hlstoplasmosis:
Most common form.
Acute form presents with mild flu like illness, pulmonary infiltrates
in chest X-ray with hilar or mediastinal lymphadenopadiy.
Chronic cavitary histoplasmosis may be seen in smokers with
underlying structural lung disease.
• Mucocutaneous histoplasmosis
Skin and oral mucosal lesions may develop secondary to
Oral lesions are particularly seen in Indian patients.
• Disseminated histoplasmosis:
Develops if CMI is very low (e.g. untreated HIV infected people or
following organ transplantation).
Common sites affected- bone marrow, spleen, liver, eyes and
6. HISTOPLASMOSIS- Laboratory Diagnosis
Sputum, aspirate from bone marrow & lymph
node, blood and biopsies from skin & mucosa.
• Direct microscopy:
Histopathological staining (PAS, Giemsa or GMS
stain) – Shows tiny oval yeast cells (2-4 µm size)
with narrow based budding within macrophages
with an underlying granulomatous response.
7. HISTOPLASMOSIS- Laboratory Diagnosis
Gold standard method of diagnosis.
Media- SDA, blood agar and BHI agar
Incubated simultaneously at 25°C and 37°C.
Produces white to buff brown colonies, consist of 2 types of
conidia or spores:
1) Tuberculate macroconidia- typical thick walls and finger-like
projections which is a characteristic feature
2) Microconidia are smaller, thin, and smooth-walled.
Gets converted into yeast form (creamy white colonies), which is
best developed in special media like Kelley's media.
8. HISTOPLASMOSIS- Laboratory Diagnosis
Antibodies in serum - detected by CFT and
Antibodies appear after 1 month of infection; hence
are more useful in chronic stage (often negative in
early course and in disseminated stage).
False positive result may occur due to past infection
or cross infection with blastomyces.
• Skin test:
May be done to demonstrate delayed type hypersensitivity
response to histoplasmin antigen, which indicates prior
9. Histoplasma capsulatum (schematic diagram)
A. Yeast form;
B. Mycelial form;
C. 2-4 µm yeast cells with narrow based budding (Giemsa stain)
D. Mold form, septate thin hyphae with tuberculate macroconidia (arrows showing)
10. HISTOPLASMOSIS- TREATMENT
• Liposomal amphotericin B
Is the antifungal agent of choice in acute pulmonary and
Recommended for chronic cavitary pulmonary
• Also known as North American blastomycosis
or Gilchrist's disease or Chicago disease
• Is a fungal infection of humans and other
animals also- dogs and cats, caused,
12. BLASTOMYCOSIS- Pathogenesis
• Transmitted by
Inhalation of the conidia of B. dermatitidis.
Spores enter into the lungs, and are engulfed by
alveolar macrophages, where they get converted
into yeast phase.
This yeast expresses a 120-kDa glycoprotein called
BAD-I (B. dermatitidis adhesin-1) which is an
essential virulence factor and also a major inducer
of cellular and humoral immune responses.
13. BLASTOMYCOSIS- Clinlcal Manifestations
• Acute pulmonary blastomycosis - Most common
• Extrapulmonary manifestations
Skin involvement - Most common extrapulmonary
form; characterized by either verrucous (more
common) or ulcerative type of skin lesions.
Osteomyelitis may develop along with contiguous soft
tissue abscesses and draining sinuses.
Prostate and epididymis involvement in men.
Central nervous system (CNS) involvement has been
reported in - 40% of AIDS patients.
Brain abscess is the usual presentation, followed by
cranial or spinal epidural abscess and meningitis.
14. BLASTOMYCOSIS- Laboratory Diagnosis
• Antibody detection: lmmunodiffusion test
specific for B. dermatitidis has been developed
against yeast phase antigens such as antigen-A,
BAD- I and ASWS antigen (alkali soluble water
• Antigen detection assay- detect Blastomyces
antigen in urine (more sensitive) and in serum is
• Molecular methods- DNA probe hybridization and
real time PCR
15. BLASTOMYCOSIS- Laboratory Diagnosis
• Histopathological staining of the tissue biopsy
specimens reveals thick-walled round yeast cells
of 8- 15 µm size with single broad-based budding
(figure of 8 appearance)
• Culture media - SDA, blood agar and BH I.
At 250C- Mycelia form containing hyphae with small
pear-shaped conidia are produced;
At 370C- mold to yeast conversion takes place.
• Skin test: done to demonstrate delayed type
hypersensitivity to blastomycin antigen.
17. BLASTOMYCOSIS- TREATMENT
• Liposomal amphotericin B
is the antifungal agent of choice in most of the cases.
in immunocompetent patients with mild
pulmonary or non CNS extrapulmonary
• Also called desert rheumatism or Valley fever
or California fever
• Is a systemic fungal disease caused by a
dimorphic soil dwelling fungus- Coccidioides
(C. immitis and C. posadasii).
19. COCCIDIOIDOMYCOSIS -Pathogenesis
• Transmitted by inhalation of arthroconidia.
• In lungs, they enlarge, become rounded, and
develop internal septations to form large sac like
structures of size up 10-200 µm called spherules-
encompass numerous endospores.
• Spherules may rupture and release packets of
endospores that can disseminate and develop
into new spherules.
• If spherules returned to artificial media or soil,
they revert back to the mycelial stage.
20. COCCIDIOIDOMYCOSIS - Clinlcal Manifestations
• Asymptomatic- in most of patients (60%).
• Pulmonary coccidioidomycosis - presents as
pneumonia, cavities, pleural effusion or nodule
• Skin lesions such as rashes or erythema nodosum and
arthritis with joint pain may appear secondary to
pulmonary infection particularly in women.
• Disseminated form:
Males and persons with low CMI (HIV infected patients
with CD4+ T cell count <250/ µI) are at higher risk.
Common sites for dissemination include skin, bone, joints,
soft tissues, and meninges.
21. COCCIDIOIDOMYCOSIS - Laboratory Diagnosis
• Histopathological staining
H and E stain, PAS or CMS of sputum or tissue biopsy
specimens demonstrates spherules which are large
sac like structures (20-80 µm size), have thick, double
refractile wall, and are filled with endospores
• Cultures on SDA –
produces mycelial growth, described as fragmented hyphae
consisting of barrel-shaped arthrospores with alternate cells
distorted (empty cells)
Coccidioides differs from other dimorphic fungi as it grows as
mold at both 25°C and 37°C in usual culture media (forms
spherules at 37°C in certain special culture media only).
Cultures are highly infectious: lead to accidental inhalation of
spores in laboratories, require biosafety level-3 precautions.
22. COCCIDIOIDOMYCOSIS - Laboratory Diagnosis
• Serology: Antibodies are detected by
immunodiffusion test and CFT.
• Skin test: It is done by fungal extaracts
(coccidioidin or spherulin);
produces at least a 5 mm induration within 48
hours after injection (delayed hypersensitivity
reaction) indicates past infection.
• Also known as South American blastomycosis,
Lutz-Splendore-de Almeida disease
• Is a systemic disease caused by the dimorphic
fungus Paracoccidioides brasiliensis.
26. Pathogenesis and clinical Manifestations
• Transmission- by inhalation of spores,
• Transform into the yeast phase in lungs.
• Occurs as two major forms.
1. Acute form (or juvenile type):
affects young adults under 30 years age.
less common variety, but more severe form, manifests as
disseminated infection involving multiple viscera and is
refractory to t/t.
2. Chronic form (or adult form):
accounts for 90% of cases
predominantly affects older men.
results from reactivation of quiescenct lung lesions.
less severe form, manifested as progressive pulmonary
disease affecting lower lobes, with fibrosis.
Skin, oral mucosal lesions and cervical lymphadenopathy
27. PARACOCCIDIOIDOMYCOSIS-Laboratory Diagnosis
• Histopathological staining - of pus, tissue biopsies or
reveals round thick-walled yeasts, which multiple narrow-
necked buds attached circumferencially giving rise to Mickeiy
mouse or pilot wheel appearance.
• Culture on SDA
yields mycelial form at 250C
converts in to yeast phase at 370C when grown in BHI agar
supplemented with blood and glutamine.
Antibodies are detected by immunodiffusion, and by ELISA,
using gp43 antigen of P. brasiliensis.
• Skin test:
demonstrates delayed hypersensitivity response against