Cutaneous Larva Migrans

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Intro & Etiology - The Wandering Worms

  • Definition: Cutaneous Larva Migrans (CLM) is a parasitic skin infection caused by animal hookworm larvae migrating within the epidermis.
  • Common Name: Creeping eruption.
  • Causative Organisms:
    • Most common: Ancylostoma braziliense (cats, dogs).
    • Others: Ancylostoma caninum (dogs).
    • 📌 Mnemonic: "Animals Bring Creeping Larva" (A. braziliense, A. caninum)
  • Transmission:
    • Direct skin penetration by infective filariform larvae.
    • Source: Soil/sand contaminated with feces from infected animals (dogs, cats).
  • Lifecycle Basics:
    • Animal reservoir (definitive hosts: dogs, cats).
    • Eggs in animal feces → larvae hatch & mature in soil.
    • Humans are accidental, dead-end hosts; larvae cannot complete development. Cutaneous Larva Migrans Lifecycle

⭐ CLM is a clinical diagnosis primarily seen in travelers to tropical/subtropical regions or those with soil/sand exposure (e.g., beaches, sandboxes).

Clinical Features - Itchy Tracks Tale

  • Incubation Period: Typically a few days to 1 week post-exposure; can extend to 1 month.
  • Hallmark Symptom: Intense, localized pruritus (itching); characteristically worse at night or with heat.

    ⭐ The intense itching is disproportionate to the visible skin signs and frequently precedes the appearance of tracks.

  • Characteristic Lesion ("Creeping Eruption"):
    • Erythematous, slightly elevated, serpiginous (snake-like), linear, or tortuous tracts or burrows.
    • Width: 2-5 mm.
    • Larval migration rate: 1-2 cm/day (can be up to 5 cm/day); larva is 1-2 cm ahead of the visible advancing track.
    • Lesion advances from one end; older part may become dry, crusted, or vesicular. Cutaneous Larva Migrans lesion on foot
  • Common Sites (areas of skin exposed to contaminated soil/sand):
    • Feet (most common: soles, interdigital spaces), buttocks, hands, thighs, anogenital region.
  • Associated Findings:
    • Vesicles or bullae along tracks.
    • Excoriations due to intense scratching.
    • Secondary bacterial infection (e.g., impetigo, cellulitis) is common.
    • Peripheral eosinophilia may be present.

Diagnosis & DDx - Spotting the Squiggles

  • Clinical Diagnosis: Key!
    • History: Exposure to soil/sand contaminated with animal feces (beaches, sandboxes).
    • Lesions: Intensely pruritic, erythematous, serpiginous, or linear raised tracks that advance a few mm to cm daily.
  • Dermoscopy: Can show brownish dots (larva) or empty tunnels.
  • Biopsy: Rarely indicated; often fails to find larva. Shows eosinophilic infiltrate.

⭐ Biopsy is usually not performed as larvae are often missed; diagnosis is overwhelmingly clinical.

Key Differential Diagnoses (DDx):

ConditionDistinguishing Features
Tinea CorporisAnnular lesions with central clearing, scaling; KOH positive
Scabies BurrowsInterdigital, wrists, axillae; nocturnal pruritus; mites/eggs on microscopy
Contact DermatitisVesicles, edema, well-demarcated to exposure area
PhytophotodermatitisStreaky, bizarre patterns; history of plant + sun exposure
Larva CurrensVery rapid track migration (cm/hour); perianal area common

Management & Prevention - Halting the Hikers

  • Natural Course: Often self-limiting; spontaneous resolution typically occurs in weeks to months.
  • Topical Therapy:
    • Thiabendazole 10-15% solution/ointment applied 2-3 times daily for 5-7 days.
  • Systemic Therapy (DOC):
    • Ivermectin: 200 µg/kg single oral dose.
    • Albendazole: 400 mg orally daily for 3-7 days.
  • Symptomatic Relief:
    • Oral antihistamines for severe pruritus.
    • Topical corticosteroids for inflammation and itching.
  • Secondary Infections: Treat with appropriate antibiotics if present.
  • Prevention:
    • Wear footwear on beaches, especially in known endemic areas.
    • Use protective barriers (e.g., towels) when sitting/lying on sand.
    • Regular deworming of dogs and cats (reservoir hosts).

⭐ Ivermectin is the drug of choice for systemic therapy due to its high efficacy and excellent tolerability.

High‑Yield Points - ⚡ Biggest Takeaways

  • Caused by hookworm larvae (esp. Ancylostoma braziliense) from fecal-contaminated soil.
  • Characterized by intensely pruritic, serpiginous, erythematous tracts ("creeping eruption").
  • Most common on feet, buttocks, hands from direct skin contact with contaminated surfaces.
  • Larva migrates 1-2 cm daily, visibly extending the track.
  • Diagnosis is primarily clinical, based on the characteristic migratory lesions.
  • Treatment: Oral albendazole or ivermectin are first-line; topical thiabendazole is an alternative.
  • Often self-limiting; treatment alleviates severe itching & reduces secondary infection risk from scratching.

Practice Questions: Cutaneous Larva Migrans

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