Scabies (sarcoptic mange)

Ectoparasitic dermatoses & Contagious skin condition caused by human itch mite Sarcoptes scabiei var. hominis (belongs to arthropod class Arachnida family Sarcoptidae) . 

Water washed disease (infections that are caused due to poor personal hygiene due to inadequate water availability and these infections decrease as a result of increasing volume of available water)

Adult female scabies mite burrow (1 to 10 mm) into Epidermis ( Mainly Stratum Corneum layer ) where they live  and deposit 2 to 3 eggs per day. Eggs hatch within 2 to 3 weeks (21-28 days) . Thus Incubation period = 21 to 28 days.

Superficial Burrows (Pathognomonic) (S shaped or Linear tracks)

Most common location in adults - Interdigital folds , Areolae , naval region , Shaft of penis , Back , elbows , Ventral wrists , Buttock  

Most common location in neonates ( Infantile scabies ) -  Palms , Soles , Face and Scalp 

Relentless Nocturnal pruritus is highly characteristic

Clinically presents in 3 forms - Classic scabies , Nodular scabies (Atypical) , very Contagious Crusted (Norwegian) scabies 

1. Classic scabies - Localized or Diffuse Hyperkeratotic plaques in palms , soles , under fingernails

2. Nodular scabies - Erythematous nodules on groin , axilla , male genitalia

3. Crusted (Norwegian) scabies - seen in immunocompromised ( HIV/AIDS , Diabetes , old age , immunosuppressive therapy , Organ transplant recipients , Leprosy ) , Down's syndrome.

Circle of Hebra (Imaginary circle connecting most common sites of involvement of scabies)

Scabies is usually Clinical diagnosis ; Punch biopsy is rarely needed to diagnose scabies.

DOC - Topical 5% Permethrin cream single overnight application from neck to toes in adults and Head to toe in children 2months age or older. Wash of with water in 8 to 14 hours . May repeat in 14 days if mites appear

Alternative - Ivermectin 0.1 to 0.2 mg/kg (usually used in outbreaks in institutions like nursing homes)

Keratolytic agents for crusting

Zoonotic scabies (Pseudoscabies) - self limiting with short incubation period and transient clinical skin signs

Scabies incognito - Topical or systemic  corticosteroids may modify clinical presentation of scabies , so that scabies mimics other dermatoses (ex- Urticaria pigmentosa)

#crackmbbs