Mycology

Question 1

Histoplasmosis

Answer 1

Mississippi and Ohio river valleys
MP filled with histoplasma (smaller than RBC)
Histo Hides (within MP)
Bird (Starling’s) or bat droppings

Question 2

Blastomycosis

Answer 2

Eastern USA and Central America
Causes inflammatory lung disease and can disseminate to skin and bone. Forms granulomatous nodules
Broad-base budding (same size as RBC)
Blasto-buds broadly

Question 3

Coccidiodomycosis

Answer 3

Southwestern USA, California
Causes pneumonia and meningitis; can disseminate to skin and bone
Case rate increases after earthquakes since spores in dust are thrown into air –> inhaled –> spherules in lung
Spherules (much larger than RBC) filled with endospores
San Joaquin Valley Fever
Desert bumps - erythema nodosum
Desert rheumatism - arthralgias

Question 4

Paracoccidiodomycosis

Answer 4

Latin America
Budding yeast with “captain’s wheel” formation (much larger than RBC)
Paracoccidio PARAsails with the captain’s wheel all the way to Latin America

Question 5

Tinea (dermatophytes)

Answer 5

Tina is the clinical name given to dermatophyte (cutaneous fungal) infections
Dermatophytes include microsporangia, Trichophyton and Epidermophyton.
Branching septate hyphae visible on KOH preparation with blue fungal stain

Question 6

Times capitis

Answer 6

Occurs on head, scalp. Associated with lymphadenopathy, alopecia, scaling

Question 7

Tina corporis

Answer 7

Occurs on torso. Characterized by erythematous scaling rings (“ringworm”) and central clearing
Can be acquired from contact with an infected cat or dog

Question 8

Tinea cruris

Answer 8

Occurs in inguinal area

Often does not show the central clearing seen in tinea corporis

Question 9

Tinea pedis

Answer 9

Three varieties

• interdigital (most common)
• moccasin distribution
• vesicular type

Question 10

Tinea unguium

Answer 10

Onychomycosis; occurs on nails

Question 11

Tinea (pityriasis) versicolor

Answer 11

Caused by Malassezia spp. (Pityrosporum spp.) a yeast like fungus (not a dermatophyte despite being called tinea)
Degradation of lipids produces acids that damage melanocytes and cause hypopigmented and/or pink patches
Can occur any time of year, but more common in the summer (hot, humid weather). “Spaghetti and meatballs” appearance on microscopy
Treatment: selenium sulfide, topical and/or oral antifungal medications

Question 12

Candida albicans

Answer 12

Dimorphic; forms pseudohyphae and budding yeasts at 20 degrees C, a germ tubes at 37 degrees C
Systemic or superficial fungal infection. Causes oral and esophageal thrush in immunocompromised (neonates, steroids, diabetes, AIDS), vulvovaginitis (diabetes, use of antibiotics), diaper rash, endocarditis (IV drug users), disseminated candidiasis (to any organ), chronic mucocutaneous candidiasis

Question 13

Candida albicans: treatment

Answer 13

Topical azole for vaginal infection
Nystatin, fluconazole or caspofungin for oral/esophageal infection
Fluconazole, caspofungin, or amphotericin B for systemic infection

Question 14

Aspergillus fumigatus

Answer 14

Septate hyphae that branch at 45 degree acute angle
Produces conidia in radiating chains at end of conidiophore
Causes invasive aspergillosis, esp in immunocompromised and those with chronic granulomatous disease
Can cause aspergillomas in pre-existing lung cavities, esp after TB infection
Some species of Aspergillus produce aflatoxins, which are associated with heptocellular carcinoma
Allergic bronchopulmonary aspergillosis (ABPA): hypersensitivity response associated with asthma and cystic fibrosis; may cause bronchiectasis and eosinophilia

Question 15

Cryptococcus neoformans

Answer 15

Small with narrow budding, heavily encapsulated yeast. Not dimorphic
Found in soil, pigeon droppings. Acquired through inhalation with hematogenous dissemination to meninges.
Culture on Sabouraud agar - highlighted with India ink (clear halo) and mucicarmine (red inner capsule). Latex agglutination test detects polysaccharide capsular Ag and is more specific
Causes: cryptococcosis, cryptococcal meningitis, cryptococcal encephalitis (“soap bubble” lesions in brain), primarily in immunocompromised

Question 16

Nucor and Rhizopus spp.

Answer 16

Irregular, broad, nonseptate hyphae branching at wide angles
Mucormycosis. Causes disease mostly in ketoacidotic diabetic and/or neutropenic pts (eg leukemia).
Fungi proliferate in blood vessel walls, penetrate cribiform plate and enter brain.
Rhinocerebral, frontal lobe abscess; cavernous sinus thrombosis. HA, facial pain, black necrotic eschar on face; may have CN involvement
Treatment: surgical debridement, amphotericin B

Question 17

Pneumocystis jirovecii

Answer 17

Causes pneumocystis pneumonia (PCP), a diffuse interstitial pneumonia. Diffuse, bilateral ground-glass opacities on CXR/CT
Yeast like fungus. Inhaled. Most infections are asymptomatic
Immunosuppression (AIDS) predisposes to disease.
Diagnosed by lung biopsy or lavage. Disc-shaped yeast seen on methenamine silver stain of lung tissue
Treatment/prophylaxis: TMP-SMX, pentamidine, dapsone (prophylaxis only), atovaquone. Start prophylaxis when CD4+ count drops to

Question 18

Sporothrix schenckii

Answer 18

Sporotrichosis. Dimorphic, cigar shaped budding yeast that grows in branching hyphae with rosettes of conidia; lives on vegetation. When spores are traumatically introduced into the skin, typically by a thorn (rose gardener’s disease) causes local pustule or ulcer with nodules along draining lymphatic system (ascending lymphangitis). Disseminated disease possible in immunocompromised host.
Treatment: itraconazole or potassium iodide

Question 19

Systemic mycoses

Answer 19

Can cause pneumonia and can disseminate
Caused by dimorphic fungi: cold = mold and heat = yeast
The only exception is coccidiodomycosis, which is a spherules (not yeast) in tissue
Treatment: flu console or itraconazole for local infection; amphotericin B for systemic infections
Systemic mycoses can form granulomas (like TB) but cannot be transmitted person to person (unlike TB)