Histoplasma capsulatum, a dimorphic fungus found in soil heavily contaminated with bird droppings, is identified in tissue biopsies by which of the following characteristics?

Oval budding yeasts within macrophages

Single-cell yeasts with pseudohyphae

Amphotericin B toxicity can be lowered by:

Using Liposomal delivery systems

Administering with saline hydration

An 34-year-old male HIV patient on c-A presents with seizures and a unilateral facial nerve palsy. The CT scan shows a ring-enhancing lesion. What is the best treatment?

Sulphadiazine, pyrimethamine and Leucovorin

A 60-year-old female with a history of diabetes presents with nasal congestion, facial pain, and black necrotic patches on the palate. What is the most likely diagnosis?

Granulomatosis with Polyangiitis (GPA)

Fungal Infections for NEET-PG: High-Yield Internal Medicine Lessons

Fungal Infections Overview - Fungus Among Us

Types:
- Yeasts (e.g., Candida): Unicellular, reproduce by budding.
- Molds (e.g., Aspergillus): Multicellular, form hyphae.
- Dimorphic: Yeast form at 37°C (body/tissue), mold form at 25°C (environment). 📌 "Mold in cold, Yeast in heat."
Key Structures:
- Cell Wall: Chitin, glucans.
- Cell Membrane: Ergosterol.

⭐ Ergosterol in the fungal cell membrane is a primary target for many antifungal drugs (e.g., Amphotericin B, Azoles).

Superficial & Cutaneous Mycoses - Itchy & Scratchy Crew

Dermatophytes: Keratinophilic fungi. Genera: Trichophyton, Microsporum, Epidermophyton.
- Cause Tinea (ringworm): capitis (scalp), corporis (body), cruris (groin), pedis (foot), unguium (nail).
- Diagnosis: KOH mount (segmented hyphae).
Malassezia furfur: Pityriasis (Tinea) versicolor.
- Hypo/hyperpigmented scaling macules; often on trunk.
- KOH: "Spaghetti & meatballs" (yeast & hyphae).
Cutaneous Candidiasis: Candida albicans.
- Intertrigo, diaper dermatitis. Erythematous plaques, satellite pustules.

⭐ Malassezia furfur causes Tinea versicolor, is a lipophilic yeast (not a dermatophyte), and lesions typically fluoresce yellow-green under Wood's lamp.

Systemic Dimorphic Mycoses - Shape-Shifting Spores

Fungus	Endemic Area	Morphology (Yeast Form)	Key Clinical Findings
Histoplasma	Ohio/Mississippi river valleys (bird/bat guano)	Small, oval; intracellular in macrophages	Pneumonia (often asymptomatic/mild), dissemination in IC
Blastomyces	Eastern/Central US (decaying organic matter)	Large, broad-based budding yeast	Pneumonia, skin (verrucous ulcers), bone lesions
Coccidioides	Southwestern US, N. Mexico (desert soil)	Spherules containing endospores	Valley fever (flu-like), erythema nodosum, meningitis

Morphology of endemic fungal infections with yeasts

⭐ Histoplasma capsulatum is typically found intracellularly within macrophages and can mimic TB.

Opportunistic Mycoses - Immune Busters

Organism	Key Disease(s)	Dx Highlights	Image Placeholder Query
Candida	Thrush, esophagitis, disseminated dz.	Pseudohyphae, budding yeast; culture	"Candida albicans microscopy"
Aspergillus	ABPA, aspergilloma, invasive dz.	Septate hyphae, acute (45°) angle; Galactomannan.	"Aspergillus hyphae microscopy"
Cryptococcus neoformans	Meningitis (CD4 < 100); pneumonia.	India ink (capsule); Cryptococcal antigen (CrAg) test.	"Cryptococcus neoformans India ink stain"
Mucor / Rhizopus	Rhino-orbital-cerebral (DKA); pulmonary.	Broad, non-septate hyphae, right-angle (90°).	"Mucor hyphae microscopy"
Pneumocystis jirovecii (PJP)	Pneumonia (CD4 < 200). Prophylaxis.	Cysts on silver stain (GMS).	"Pneumocystis jirovecii cysts silver stain"

Antifungal Agents - Foe Finishers

Class	MOA	Spectrum	Key ADRs	Clinical Pearls
Polyenes	Binds ergosterol, ↑ cell permeability	Broad (Candida, Aspergillus, Crypto)	Nephrotoxicity, infusion reactions, ↓K⁺, ↓Mg²⁺	Amphotericin B (AmB)
Azoles	Inhibit ergosterol synthesis (CYP450)	Broad (Candida, Crypto, Dermatophytes)	Hepatotoxicity, drug interactions (CYP inh.)	Fluconazole (Candida), Itraconazole (Aspergillus, dimorphic), Voriconazole (Aspergillus)
Echinocandins	Inhibit β-(1,3)-D-glucan synthesis	Candida, Aspergillus	GI upset, flushing	Caspofungin, Micafungin; good for azole-resistant Candida
Flucytosine	Inhibits DNA/RNA synthesis	Cryptococcus, Candida (combo therapy)	Bone marrow suppression, hepatotoxicity	📌 "5-FC = Five-Fluorocytosine causes Fatty liver, Flatulence, Fall in Hb"

High‑Yield Points - ⚡ Biggest Takeaways

Mucormycosis: Uncontrolled diabetes, rhino-orbital-cerebral, non-septate hyphae, Amphotericin B.

Aspergillosis: ABPA (asthma, ↑IgE), Aspergilloma, Invasive (immunocompromised, Voriconazole), septate hyphae.

Candidiasis: Thrush, esophagitis; disseminated in immunocompromised. Fluconazole. C. auris (MDR).

Cryptococcal meningitis: HIV/AIDS (CD4 <100), India ink, CrAg test, Amphotericin B + Flucytosine.

PCP (P. jirovecii): HIV/AIDS (CD4 <200), bilateral infiltrates, TMP-SMX (treatment/prophylaxis).

Histoplasmosis: Mimics TB, bird/bat droppings, disseminated in immunocompromised, Itraconazole.

Sporotrichosis: "Rose gardener's disease", lymphocutaneous spread, Itraconazole.

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Fungal Infections