Common Hair shaft infections

Pediculosis pubis

Synonym

• Pthirus pubis or Phthirus pubis 

• Pubic lice

 Note: As it can involve other hair bearing areas like eyelashes, beard, body; public lice is an inappropriate term. Crab lice infest coarse hair and hence, pubic hair and hair lashes are involved, not silky scalp hairs. Crab lice survive for 2 days without human host

Presentation
Typically present with pruritus in the pubic region

• It is a STD

• Crab lice may be seen clinging to the base of hairs

• Macula caerulea: Asymptomatic lesions on the trunk and thighs. They are slate-gray to bluish (cerulea= blue) macules. The breakdown of bilirubin to biliverdin by enzymes in louse saliva has been postulated to cause these lesions (PGI question)

Pediculosis pubis (Source: Wikipedia)

Treatment

• Permethrin (5% better than 1%). As with head lice, all topical insecticides should be applied on two occasions, 1 week apart to target newly hached eggs
• Shaving of hair

Pediculosis ciliaris

Infestation of lid margins by the crab louse. 

Note: In Pediculosis capitis, ie infestation by head lice, the lashes are rarely involved 

Presentation:

• Due to genital-to-eye transmission, possibly on bedding and towels 

• Madarosis

• Conjunctival hyperaemia 

• Superficial punctate keratopathy 

• Bites leave red inflamed areas on lid margins 

Treatment

• Remove lice, nits,casts by forceps 

• Application of petrolatum jelly to the lid margins will suffocate lice (applied twice daily for at least 2 weeks) 

• Oral ivermectin on days 1 and 8 can be used 

• 1% permethrin very carefully on closed eyelids

Pediculosis capitis

• Infection of the head hair and scalp by the head louse (Pediculus humanus capitis)

• Common, especially in children

• Commonest cause for posterior cervical lymphadenitis in children (MCQ)

• Treatment is 1% permethrin 

Trichomycosis axillaris

• It is a misnomer (no fungus)

• Bacterial infection by corynebacterium tenuis (Comedk 2015 question)

Treatment
Shaving

(Source: Global skin atlas)

Piedra

• Superficial fungal infection of hair shafts. "Piedra" means “stone”, due to the fungal nodules along the hair shaft

• 2 types – black piedra (caused by Piedra Hortae) and white piedra ( caused by Trichosporon beigelii) (NBE question) 

White piedra (Source: ijdvl)










Black Piedra (Source: ijdvl)

Treatment: Shaving