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Scabies pathogenesis and clinical findings

Scabies: Pathogenesis and clinical findings Direct person-person transmission of Sarcoptes Scabiei var. hominis to new host Fertilized females secrete proteolytic enzymes that allow them to burrow through the stratum corneum (2 mm/day) Authors: Heena Singh Amanda Eslinger Nirav Saini Reviewers: Shahab Marzoughi Danny Guo Yan Yu Richard Haber* * MD at time of publication Mechanical irritation and immunological reaction Mast cell activation and histamine release Itch (> 10 Mites) Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale Females lay 2-3 ova/day which hatch in the stratum corneum in pockets after 3 days The larvae molt and mature for 2 weeks and mate within the pockets of the stratum corneum Following mating, female mites begin burrowing Cycle is propagated as new female mites create more burrows in stratum corneum Superficial, Linear, Tortuous (i.e., Twisted) +/- Scaly Burrows ↑ Exposure to mite antigens such as Sar s 14.3 and Sar s 14.2 Type 2 helper T-cells produce proteins IL-4, IL-5, IL-13 ↑ Serum Immunoglobulin G & E ↑ Eosinophil Count in Peripheral Blood Inappropriate T helper-type immune response in skin (mechanism unknown) Antigens forming from mite feces, ova, or decomposing bodies Type IV hypersensitivity reaction (delayed immune response 2-4 weeks following initial contact) Skin barrier dysfunction from inflammation and histamine release Pre-existing immunosuppression Chronic inflammatory response Allergic reaction to ↑ mite activity at night Uncontrollable Itch (Worse At Night) + Excoriations (Scratch Marks) Urticarial (Hive-Like) Crusted Papules Eczematous Plaques Skin breakdown Opening for bacteria (commonly S. aureus) 2° Bacterial infection Pustules Legend: Pathophysiology Mechanism Sign/Symptom/Lab Finding Complications Published Oct 17, 2013; updated Jun 9, 2024 on www.thecalgaryguide.com