Mycology

Question 1

dimorphic fungi means

Answer 1

cold (20 Celsius) = mold

Heat (37 Celsius) = yeast

Question 2

Fungi tx

Answer 2

Fluconazole or itraconazole for local infection

amphotericin B for systemic infection

Question 3

Fungi that is from bird/bath droppings in the mississippi and ohio river valleys

Answer 3

Histoplasmosis

Histo hides within macrophages - macrophage filled with histoplasma

presents with palatal/tongue ulcers

Splenomegaly

Question 4

Fungi that is from eastern and central US. Causes inflammatory lung disease and can disseminate to skin/bone

Answer 4

Broad based budding “blasto buds broadly”

Verrucous skin lesions can simulate SCC

Forms granulomatous nodules

Question 5

Fungi from southwestern US, california that can cause erythema nodosum (desert bumps)

Answer 5

Coccidioidomycosis

Spherule filled with endospores

Disseminates to skin/bone

Erythema nodosum (desert bumps) or multiforme Arthralgias (desert rheumatism)

Can cause meningitis

Question 6

Fungi from Latin America that has a “captains wheel” formation

Answer 6

Paracoccidioidomycosis

Inflammatory lung dz, can disseminate to skin/bone, verrucous skin lesions , forms granulomatous nodules

Question 7

Tinea (dermatophytes)

Answer 7

Cutaneous fungal infections

includes microsporum, trichophyton, epidermophyton

Branching septate hyphae visible on KOH preparatin with blue fungal stain

Associated with pruritus

Question 8

Tinea capitis

Answer 8

cutaneous fungal infection of head and scalp

lymphadenopathy , alopecia, scaling

Question 9

Tinea Corporis

Answer 9

cutaneous fungal infection of the forso

erythematous scaling rings “ringworm” and central clearing

acquired from contact with an infected cat or dog

Question 10

Tinea Cruris

Answer 10

cutaneous fungal infection of the Inguinal area

No central clearing

Spares scrotum

Question 11

Tinea pedis

Answer 11

cutaneous fungal infection of the foot

Three varieties:

interdigital (most common)
Moccasin distribution
Vesicular type

Question 12

Tinea unguium

Answer 12

Onychomycosis

cutaneous fungal infection of the nails

Question 13

Tinea (pityriasis) versicolor

Answer 13

Caused by Malassezia spp.

This is a YEAST like fungus. It is not a dermatophyte eventhough it is called “tinea”

Degradation of lipids produces acids that damage melanocytes and cause hypopigmented, hyperpigmented, and or pink pathces

More common in summer because its hot and humid

“spaghetti and meatballs” appearance on microscopy

Question 14

This is a dimorphic fungi that forms pseudohyphae and budding yeast at 20 celsius and germ tubes at 37 celsius.

Answer 14

Candida albicans

Thrush, vulvovaginitis, diaper rash, endocarditis (IV drug users), disseminated candidiasis, chronic mucocutaneous candidiasis

Question 15

This is a monomorphic fungi with septate hyphae that branch at 45 degree acute angles

Answer 15

Aspergillus fumigatus

Invasive aspergillosis in immunocompromised patients, neutrophil dysfunction, aspergillomas, some produce aflatoxins which are associated with hepatocellular carcinoma

Allergic bronchopulmonary aspergillosis (ABPA) - hypersensitivity response associated with asthma and CF

May cause bronchiectasis and eosinophilia

Question 16

This is a a heavily encapsulated yeast that is not dimorphic. It is found in soil and pigeon droppings

Answer 16

Cryptococcus neoformans

Inhalation with hematogenous dissemination to meninges

Culture on Sabouraud agar
Highlight with india ink to see clear halo
Mucicarmine shows red inner capsule
Latex agglutination test detects polysaccharide capsular antigen

Cryptococcosis, cryptococcal meningitis, cryptococcal encephalitis ( “soap bubble” lesions in brain), primarily in immunocompromised

Question 17

This fungi has irregular, broad, nonseptate hyphae branching at wide angles

Answer 17

Mucor and Rhizopus spp

Causes mucormycosis, mostly in ketoacidotic diabetic and or neutropenic patients

inhale spores –> fungi proliferates in blood vessel walls –> penetrate cribriform plate –> enters brain

Rhinocerebral, frontal lobe abscess
Cavernous sinus thrombosis

Headache, facial pain, black necrotic eschar on face, may have cranial nerve involvement

Question 18

Yeast like fungus that causes diffuse interstitial pneumonia.

Answer 18

Pneumocystis jirovecii

Causes Pneumocystis pneumonia (PCP)

Diffuse bilateral ground glass opacities on CXR/CT with pneumatoceles

Disc shaped yeast seen on methenamine silver stain of lung tissue

Major concern in HIV patients with CD4+ count <200

Question 19

Dimorphic cigar shaped budding yeast that grows in branching hyphae with rosettes of conidia. Lives on vegetation and is called the “rose gardeners disease”

Answer 19

Sporothrix schenckii

causes sporotrichosis - spores are traumatically introduced into the skin by a thorn and causes local pustule or ulcer with nodules along draining lymphatics (ascending lymphangitis)

Disseminated disease possible in immunocompromised host

Tx with itraconazole or potassium iodide