Is lichen simplex chronicus a finding in scabies treatment?

Lichen Simplex Chronicus in Scabies: Diagnosis and Treatment

Lichen simplex chronicus (LSC) can occur as a complication of scabies due to chronic scratching and is not a finding on biopsy of scabies itself, but rather a secondary condition that develops from the itch-scratch cycle. 1, 2

Relationship Between Scabies and Lichen Simplex Chronicus

• Scabies is a parasitic infestation caused by the mite Sarcoptes scabiei, typically treated with permethrin 5% cream or oral ivermectin 3, 4
• LSC develops as a secondary condition from repetitive scratching or rubbing of the skin in response to the intense pruritus caused by scabies 1, 2
• LSC presents as hyperpigmentation and thickening (lichenification) of the skin with variable scaling, rather than being a primary finding in scabies 1, 5
• The pathophysiology involves a chronic itch-scratch cycle that leads to skin thickening over time 2

Diagnostic Considerations

• LSC is diagnosed clinically by its characteristic appearance of thickened, hyperpigmented skin with accentuated skin markings 6, 5
• On biopsy, LSC shows epidermal hyperplasia, hyperkeratosis, and a variable inflammatory infiltrate - distinct from the findings of scabies mites or burrows 2, 5
• Scabies diagnosis focuses on identifying the mite, eggs, or fecal matter (scybala) in skin scrapings, while LSC is a clinical diagnosis based on the characteristic appearance of lichenified skin 3, 7
• It's important to distinguish between primary scabies findings and secondary LSC changes, as they require different treatment approaches 2

Treatment Approach

• First treat the underlying scabies infestation:

  • First-line: Permethrin 5% cream applied to all areas of the body from neck down and washed off after 8-14 hours 3, 4
  • Alternative: Oral ivermectin 200 μg/kg, repeated in 2 weeks 3, 4

• Then address the lichen simplex chronicus:

  • Topical ultrapotent corticosteroids are the first-line treatment for LSC 8, 5
  • Treatment should continue until clinical improvement of the lichenified areas 8, 5
  • Breaking the itch-scratch cycle is essential for successful management 2, 5

Management Pitfalls to Avoid

• Failing to identify and treat the underlying scabies infestation will lead to persistent LSC 2
• Misdiagnosing LSC as purely psychogenic pruritus when there is an underlying dermatological cause like scabies 2
• Not treating all close contacts for scabies simultaneously, which can lead to reinfestation and persistent symptoms 3, 4
• Expecting immediate resolution of LSC after scabies treatment - the lichenified skin changes may take weeks to months to improve even after successful eradication of scabies 4, 2

Follow-up Considerations

• Pruritus from scabies may persist for up to 2 weeks after successful treatment 3, 4
• LSC changes will take longer to resolve even after the scabies infestation is cleared 2, 5
• Consider retreatment for scabies if symptoms persist beyond 2 weeks or if live mites are observed 3, 4
• Long-term follow-up may be necessary for patients with persistent LSC despite successful scabies treatment 8, 2

By understanding that LSC is a secondary complication of scabies rather than a primary finding on biopsy, clinicians can implement appropriate treatment strategies targeting both the underlying infestation and the resulting skin changes.