Fungal and Parasitic Infections

Fungal Arthritis: Overview - Not-So-Fun Guys

• Rare, indolent, monoarticular; diagnosis often delayed.
• Common Pathogens:
  • Candida albicans (most common; post-op, IVDU, disseminated)
  • Aspergillus spp. (immunocompromised)
  • Dimorphic: Blastomyces, Coccidioides, Sporothrix (rose gardener's)
• Key Risk Factors:
  • Immunosuppression (HIV, steroids, DM, TNF-α inhibitors)
  • Prosthetic joints, IV drug use
  • Direct inoculation: injections, trauma, surgery
• Clinical: Chronic pain, swelling, warmth, ↓ROM; minimal systemic signs.
• Diagnosis: Synovial fluid (↑WBC, culture, stains: PAS, GMS); Biopsy (histology & culture gold standard).
• Management: Systemic antifungals (Ampho B, azoles) + surgical debridement.

⭐ Candida is the most common fungal arthritis, often linked to disseminated candidiasis or iatrogenic inoculation (e.g., injections).

Fungal Arthritis: Dx & Rx - Diagnosis & Duel

• Diagnosis (Dx):
  • Presentation: Insidious onset, chronic, often monoarticular (knee common). Risk: Immunocompromised, IVDU, trauma, prior surgery/injection.
  • Synovial Fluid:
    • WBC: 10,000-40,000/µL (mononuclear predominance).
    • Glucose: ↓.
    • Culture: Gold standard (Sabouraud agar). Prolonged incubation (2-4 weeks).
    • Stains: KOH prep, Gram (Candida), Giemsa, PAS, GMS.
  • Synovial Biopsy: Higher diagnostic yield for histology (granulomas, fungal elements) & culture.
  • Imaging: X-ray (late: juxta-articular osteopenia, erosions, joint space narrowing). MRI (early: synovitis, effusions).
  • Adjuncts: Serum (1,3)-β-D-glucan. Galactomannan (Aspergillus).
• Treatment (Rx) - "Duel": Prolonged Antifungals + Surgical Debridement.
  • Candida spp.: Fluconazole or Echinocandin (e.g., Caspofungin). Amphotericin B (lipid) for severe/resistant.
  • Aspergillus spp.: Voriconazole (DOC).
  • Sporothrix schenckii: Itraconazole (DOC for osteoarticular).
  • Duration: Typically 6-12 months, often longer.

⭐ Candida albicans is the most common fungal pathogen causing arthritis, frequently resulting from hematogenous dissemination or direct inoculation.

Parasitic Arthritis: Overview - Unwelcome Guests

• Pathogenesis: Joint inflammation triggered by:
  • Direct parasitic invasion (e.g., Dracunculus medinensis).
  • Immune-mediated reactions (e.g., immune complex deposition, hypersensitivity).
  • Larval migration effects.
• Common Causative Agents:
  • Helminths: Echinococcus granulosus (hydatid disease), Schistosoma spp., Filarial worms (Wuchereria, Brugia), Strongyloides stercoralis, Toxocara spp.
  • Protozoa (less common): Giardia lamblia (reactive arthritis).
• Clinical Pointers:
  • Typically monoarticular, but can be oligo- or polyarticular.
  • Migratory arthralgia, chronic synovitis possible.
  • Peripheral eosinophilia is a significant indicator.
• Diagnostic Approach:
  • Synovial fluid analysis: Look for eosinophils, rarely larvae/ova.
  • Serology for specific parasites.
  • Imaging (X-ray, USG, CT/MRI): May show cysts, calcifications.
  • Biopsy (synovial/muscle) if diagnosis is elusive.

⭐ Osseous hydatid disease (Echinococcus granulosus) can present as bone cysts that erode into adjacent joints, mimicking primary arthritis or osteomyelitis.

Parasitic Arthritis: Dx & Rx - Detection & Defense

• Etiology & Clues (Detection):
  • Protozoa: E. histolytica, Giardia (reactive).
  • Helminths:
    • Nematodes: Dracunculus (direct, calcified), Strongyloides, Filarial (reactive, migratory).
    • Cestodes: Echinococcus (hydatid, direct).
    • Trematodes: Schistosomiasis (reactive).
  • Clues: Mono/polyarthritis, travel Hx, eosinophilia, primary infection signs.
• Diagnosis (Dx):
  • Synovial fluid: Inflammatory, ↑eosinophils (key!), parasite microscopy (rare).
  • Serology; Stool/Urine exam (ova, cysts).
  • Imaging: X-ray (calcified worms, lytic lesions), USG/MRI.
  • Biopsy: If diagnosis elusive.
• Treatment (Rx - Defense):
  • Targeted antiparasitics: Metronidazole, Albendazole, Praziquantel, Ivermectin.
  • Symptomatic: NSAIDs; Corticosteroids (cautious use).
  • Surgical: Hydatid cyst/Guinea worm removal.

⭐ Peripheral eosinophilia is a significant clue for helminthic arthritis; synovial fluid eosinophilia, though less common, is more specific.

High‑Yield Points - ⚡ Biggest Takeaways

• Fungal arthritis: Often indolent, monoarticular; Candida most common, especially in immunocompromised or with prosthetics.
• Fungal osteomyelitis: Frequently affects vertebrae; Aspergillus common in immunocompromised individuals.
• Sporothrix schenckii: "Rose gardener's disease", characterized by lymphocutaneous spread to joints.
• Madura foot (Mycetoma): Chronic infection with sinus tracts discharging colored grains (sulfur granules).
• Parasitic bone disease: Rare; includes Echinococcus (hydatid cysts in bone) and Cysticercosis (intramuscular cysts).
• Diagnosis: Relies on biopsy and culture (e.g., Sabouraud agar for fungi) for definitive identification.
• Treatment: Involves prolonged specific antimicrobial therapy (antifungals/antiparasitics) and often surgical debridement.