Fungi

Question 1

Histoplasma Capsulatum (Histoplasmosis): where is it located, how is it transmitted, and what does it look like?

Answer 1

• midwestern/central U.S. (Mississippi/Ohio Rivers)
• from bird/bat poop (recently in cave/chicken coop)
• inhaled spores, phagocytosed yeast (macrophages with intracellular oval bodies on KOH prep)

Dimorphic! (mold in the cold/yeast in the heat)

Question 2

Histoplasm Capsulatum (Histoplasmosis): what four things does it cause clinically? (PECH)

Answer 2

• MIMICS TUBERCULOSIS (pneumonia/granuloma formation in lungs, erythema nodosum of shins. calcified lung deposits)

disseminated histoplasmosis (immunocompromised) can cause hepatosplenomegaly

Question 3

Blastomyces Dermatitidis: where is it located, how is it transmitted, and what does it look like?

Answer 3

• Southern/Eastern US (Great Lakes/Ohio River Valley)
• inhaled as mold spore (aerosol/dimorphic)
• broad based budding; same size as RBC

Question 4

Blastomyces Dermatitidis: what does it cause clinically?

Answer 4

• patchy alveolar infiltrate on Lung X-Rays
• pulmonary granuloma formation (lesions and cavities)
• disseminated (immunocompromised) –> skin (lesions), genitourinary problems, bone (osteomyelitis)

Question 5

Coccidioides Immitis (San Joaquin Fever): where is it located, how is it transmitted, and what does it look like?

Answer 5

• California and Southwest US
• inhaled mold spores (earthquakes inc. spread)
• Dimorphic; forms spherules filled with endospores inside the lung (larger than RBCs)

Question 6

Coccidioides Immitis (San Joaquin Fever): what does it cause clinically?

Answer 6

• self-limited community acquired pneumonia (cough/fever/arthraligia)
• unilateral infiltrate on chest X-Ray that is unremarkable in half of affected patients; associated with erythema nodosum on shins
• disseminated (immunocompromised) can cause skin and bone lesions as well as cause MENINGITIS

Question 7

Paracoccidioides Brasilinesis: where is it located, how is it transmitted, and what does it look like?

Answer 7

• Brazil and South America
• transmitted as respiratory droplets
• Dimorphic; yeast looks like a “Captains Wheel”; larger than RBCs

Question 8

Paracoccidioides Brasilinesis: what does it cause clinically?

Answer 8

• leads to pulmonary granuloma formation
• disseminated causes cervical lymphadenopathy
• chronically presents as mucocutaneous lesions of the mouth

Question 9

Malassezia furfur (Pityriasis versicolor): what does it look like and where is it mainly found?

Answer 9

• lipid-dependent fungus
• “spaghetti and meatballs” appearance on KOH prep
• stays only in the stratum corneum (most superficial layer) –> trunk and upper extremities

Question 10

Malassezia furfur (Pityriasis versicolor): what does it cause clinically and who is it commonly associated with?

Answer 10

• hypo/hyperpigmentation on trunk and upper extremities (produces melanocyte damaging acids via lipid degradation)
• associated with NICU neonates receiving Total Parenteral Nutrition via Catheters (inc. lipid transfusions)

Question 11

Dermatophytes (Tinea –> RINGWORM): where is it found and how is it acquired?

Answer 11

• acquired from infected pets and is commonly associated with swimmers/wrestlers (athletes)
• hypae can be visualized on KOH skin scrap prep
• most infections are pruritic (cause itching)

Question 12

What does Tinea Capitis, Tinea Corporis, Tinea Cruris, and Tinea Pedis cause?

Answer 12

T. Capitis –> head and scalp infection
T. Corporis –> body infection
T. Cruris –> groin (“Jock’s Itch”)
T. Pedis –> foot (“Athlete’s Foot”)

Question 13

Sporothrix Schenckii (Rose Gardener’s Disease): how is it acquired, what does it look like, and what does it cause clinically?

Answer 13

• found in soil and plant matter, and is commonly transmitted by cuts from Rosebush thorns
• dimorphic; yeast looks like elongated cigar-shapes w/granulomas
• causes local ulcer @ site of infection, and can infect lymphatics causing ascending lymphatic infection (subcutaneous)

Question 14

Candida Albicans: what does it look like and what is a positive test for it?

Answer 14

• dimorphic BUT –> yeast in cold and mold in heat
• CATALASE (+)
• usually normal GI tract flora

Question 15

Candida Albicans: what does it cause clinically? (4) - (DR/OT/VI/IE)

Answer 15

1. diaper rash in infants
2. disseminated disease in immunocompromised
   
   • oral thrush, HIV-associated esophagitis (CD4 < 200)
   • AIDS-defining illness
3. vulva/vagina infection
   
   • vulvar pruritis, thick white vaginal discharge
   • pH remains NORMAL
   • inc. risk in diabetics, birth control, antibiotics
4. infective endocarditis of tricuspid valve
   
   • IV drugs, prosthetic valves, indwelling lines

Question 16

Aspergillus fumigatus: how is it transmitted, what does it look like, and what is a positive test for it?

Answer 16

• condiophores w/fruiting bodies (spores are inhaled)
• septate hyphae that form 45 degree branching angles
• CATALASE (+)

A. flavus toxins associated with hepatocellular carcinoma and are found in nuts, wheat, peanuts

Question 17

Aspergillus fumigatus: infections (ABPA, balls, angioinvasion - RER))

Answer 17

1. Allergic Bronchopulmonary Aspergillosis
   
   • Type I hypersensitivity
   • wheezing, fever, inc. IgE production (CF/asthma)
2. Fungus Balls
   
   • form in people that have preexisting lung cavities
   • fever, hemoptysis, cough
   • GRAVITY-dependent positioning (X-Rays)
3. Angiovasive Aspergillosis (invade BV and dissems)
   
   • immunocompromised pts (neutropenia)
   • renal failure, endocarditis, ring enhancing lesions
   • also paranasal sinus inf. w/necrosis around nose

Question 18

Cryptococcus neoformans: what does it look like, how is it acquired, and what is a positive test for it?

Answer 18

• yeast cells heavily encapsulated (repeating polysaccharide capsular Ags) –> antiphagocytic
• enters body via inhalation (soil and pigeon poop)
• UREASE (+)

Question 19

Cryptococcus neoformans: what does it cause clinically and what do the India Ink and Latex Agglutination Tests show?

Answer 19

• pulmonary often asymptomatic (cough, fever)
• mainly seen in immunocompromised
  • # 1 cause of fungal meningitis (fever/neck stiffness)
  • “Soap Bubble” lesions in gray matter of brain

India Ink: white “halo” capsules on black background
- CSF testing
LA Test: detects polysacc. Ag (serum and CSF)

Question 20

Mucormycetes (Mucor and Rhizopus): how is it acquired, what does it look like, and what is the most common predisposing factor for it?

Answer 20

• spore inhalation, proliferate in BVs and enter brain through CRIBIFORM plate
• molds form neoseptate rods with 90 degree wide angle branches
• Rhizopus STRONGLY associated with Diabetic Ketoacidosis (also bread molds and diabetes)

Question 21

Mucormycetes (Mucor and Rhizopus): what does it cause clinically?

Answer 21

frontal lobe abscess that causes necrosis of the surrounding tissue

• necrosis of nasal cavity (black eschar on the palate or turbinates)

Question 22

Pneumocystis jirovecii and HIV

Answer 22

• P. jirovecii pneumonia is the MOST PREVALENT opportunistic infection in HIV patients (AIDS-defining illness)
• infects immunocompromised patients almost exclusively (CD4+ < 200)

Question 23

Pneumocystis jirovecii: what does it cause clinically, and what does it look like on X-Rays and biopsy?

Answer 23

• opportunistic fungal pneumonia
• chest X-Ray: “ground-glass” infiltrates; silver stain of lung biopsy/bronchoalveolar lavage shows DISC-SHAPED YEAST (crushed ping pong ball appearance)