Mycology

Question 1

What are the systemic mycoses (4)?

Answer 1

Histoplasmosis, Blastomycosis, Coccidioidomycosis, Paracoccidioidomycosis

Question 2

What disease can the systemic mycoses all cause?

Answer 2

Pneumonia.

Can all disseminate (hence the name, systemic mycoses)

Question 3

What is a common morphological trait among the systemic mycoses?

Answer 3

Thermal dimorphism -

Cold (20°C) = mold

Hot (37°) = yeast

Exception: Coccidioidomycosis, which is a spherule in tissue.

Question 4

What is the treatment for local and disseminated infection with the systemic mycoses?

Answer 4

Fluconazole or itraconazole for local infection.

Amphotericin B for systemic infection

Question 5

What disease can systemic mycoses mimic?

Answer 5

Can mimic TB (granuloma formation)

But NO person to person transmission!

Question 6

A patient who recently traveled to the Mississippi and Ohio River valleys presents with pneumonia.

Blood smear shows macrophages filled with an organism.

Culture grows dimorphic fungi.

Diagnosis?

What is the source of infection?

Answer 6

Histoplasmosis.

Histo hides (within macrophages). Organisms smaller than RBCs.

Bird or bat droppings

Dimorphic fungi causing pneumonia from mississippi or ohio river valleys.

Question 7

A patient from Michigan presents with Pneumonia and granulomatous nodules on the skin.

A biopsy of the skin (shown below) finds a broad-based budding fungi that is similar in size to a RBC.

Culture shows a thermally dimorphic fungi.

Answer 7

Blastomycosis

Blasto buds broadly.

States east of Mississippi river and Central America.

Inflammatory lung disease and disseminates to skin and bone. Forms granulomatous nodules.

Question 8

Patient from California presents after an earthquake with pneumonia and meningitis.

Culture of the CSF shows spherules filled with endospores.

Answer 8

Coccidioidomycosis.

From Southwestern United States, California.

Coccidio crowds

“(San Joaquin) Valley fever”

“Desert bumps” = erythema nodosum

“Desert rheumatism” = arthralgias

Question 9

A patient from Latin America presents with pneumonia.

Biopsy shows budding yeast with “captain’s wheel” formation that are much larger than RBCs.

Culture shows a thermally dimorphic fungi.

Answer 9

Paracoccidioidomycosis

From Latin America.

_Para_coccidio _para_sails with the _Captain’s_ _wheel_ all the way from _Latin_ _America_.

Question 10

Patient presents with hyper and hypopigmented skin patches.

A KOH stain shows organisms with a “spaghetti and meatballs” appearnce.

Answer 10

Tinea versicolor

Caused by fungus Malassezia furfur

Occurs in hot, humid weather. Degradation of lipids produce acids that damage melanocytes and cause hyper and hypopigmented patches.

Organisms have a “Spaghetti and meatball” appearance.

Question 11

How would you treat a Tinea versicolor infection?

Answer 11

Organism: Malassezia furfur

Give topical miconazole, selenium sulfide.

Question 12

What organism causes athlete’s foot, Jock itch, ringworm on body, ringworm on scalp, and onchomycosis?

Answer 12

Other tinea species - named based on location.

Tinea pedis = foot

Tinea cruris = groin

Tinea corporis = ringworm on body

Tinea capitis = ringworm on head/scalp

Tinea unguium = onchomycosis (fingernail).

Question 13

Patient presents with an itchy lesion with central clearing resembling a ring.

KOH prep shows mold hyphae, but the fungus is not dimorphic.

What organisms could this be?

Answer 13

Description classic for dermatophytes.

Microsporum, Trichophyton, Epidermophyton

Question 14

Patient presents with easily scrapable oral leukoplakia.

Answer 14

Candida albicans. Alba = white.

Systemic or superficial fungal infection.

Question 15

What are the diseases Candida albicans can cause?

Predisposing factors for each?

Answer 15

Oral and esophageal thrush in immunocompromised (neonates, steroids, diabetes, AIDS).

Vulvovaginitis (diabetes/antibiotics)

Diaper rash

Endocarditis (IV drug use)

Disseminated (any organ)

Chronic mucucutaneous candidiasis

Question 16

How do you treat Candida albicans?

Answer 16

Topical azole for vaginal

Fluconazole/caspofungin for oral/esophageal

Fluconazole, amphotericin B, or caspofungin for systemic.

Question 17

How does Candida albicans appear on microscopy?

Answer 17

Dimorphic yeast -

20°C Pseudohyphae and budding yeasts

37°C Germ tubes

Question 18

A patient with a history of TB presents with worsening respioratory symptoms.

A sputum sample shows septate hyphae that branch at 45° angles.

Diagnosis?

Answer 18

Aspregillus fumigatus

Causes invasive aspergillosis in immunocompromised/chronic granulomatous disease.

Allergic bronchopulmonary aspergillosis: Asthma and cystic fibrosis - bronchiectasis and eosinophilia.

Aspergillomas in lung cavities after TB infection.

Think A for Acute Angles in Aspergillus. Not dimorphic.

Question 19

Patient presents with hepatocellular carcinoma.

What fungal-produced toxin is associated with HCC?

Answer 19

Aflatoxins - some species of Aspergillus.

Question 20

Immunocompromised patient presents with meningitis.

CT shows “soap bubble” lesions in the brain.

How would you stain this organism?

Answer 20

Cryptococcus neoformans

Stains with India ink and mucicarmine.

Heavily encapsulated yeast, not dimorphic. Found in soil, pidgeon droppings.

Question 21

What media is required to culture Cryptococcus neoformans?

Answer 21

Sabouraud agar

Question 22

What’s a specific test for Cryptococcus neoformans?

Answer 22

Latex agglutination test - detects polysaccharide capsular antigen.

Question 23

A patient in diabetic ketoacidosis presents with headache, facial pain, and black necrotic eschar on the face.

An sample of the organism shows irregular, broad, nonseptate hyphae branching at wide angles.

Diagnosis?

Answer 23

Mucor and Rhizopus species.

Mucor: Disease mostly in ketoacidotic diabetes and leukemic patients. Fungi proliferate in blood vessel walls when there is excess glucose or ketone.

Penetrate cribiform plate and enter brain.

Rhinocerebral, frontal lobe abscesses. May have cranial nerve involvement.

Question 24

What is the treatment for mucormycosis?

Answer 24

Amphotericin B

Question 25

An immunocompromised patient presents with pneumonia with a diffuse bilateral CXR appearance.

Culture shows disc-shaped yeast on methenamine silver stain of lung tissue.

Diagnosis?

Answer 25

Pneumocystic jirovecii causing pneumocystis pneumonia (PCP)

Caused by inhaling yeast, symptomatic when immunocompromised.

Question 26

What are some prophylactic/treatment measures for Pneumocystis?

When should they be done in an AIDS patient?

Answer 26

TMP-SMX, pentamidine, dapsone (prophylaxis only), atovaquone (prophylaxis only).

Start prophylaxis when CD4 count drops < 200cells/mm³

Question 27

Patient presents with a pustule where he had been pricked by a thorn.

Microscopy shows cigar-shaped budding yeast.

Answer 27

Sporothrix schenckii causing Sporotrichosis.

A dimorphic cirag-shaped budding yeast that lives on vegetation. Traumatic introduction to skin (“rose gardener’s disease”)

Forms pustule or ulcer with nodules along draining lymphatics (ascending lymphangitis).

Question 28

What is the treatment for Sporotrichosis?

Answer 28

Treatment: Itraconazole or potassium iodide. (Rose gardener’s disease)

“Plant a rose in the pot.”

Question 29

Name the opportunistic fungal infections.

Answer 29

• Candida albicans*
• Aspergillus fumigatus*
• Cryptococcus neoformans*
• Mucor* (and Rhizopus)
• Pneumocystic jirovecii*
• Sporothrix schenckii*