Dermatology in the tropics

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NTDs

• preventative chemoTx and transmission control (PCT) ones
  • mass drug administration
    • onchocerciasis
    • lympahatic filariasis
    • schistosomiasis
    • soil-transmitted helminths
• innovative and intensified disease management (IDM) ones
  • individual care findings and case management
    • leishmaniasis
    • buruli ulcer
    • mycetoma
    • yaws
      • azithromycin is turning yaws to PCT
    • scabies
      • ivermectin is turning scabies to PCT
    • ...

skin NTDs

• new movement to integrate disease controls between NTDs that manifest with skin symptoms
  • led by WHO and community dermatologists

exanthematology

• morphology of each rash
• distribution
• sites on body

leprosy

• Mycobacterium leprae
• 20,000-25,000 new cases/year
  • mostly in India
• respiratory transmission? difficult to determine because of long incubation period
• skin + peripheral nerve manifestation
  • M. leprae has affinity to Schwann cells and destroy them
• clinical manifestation differs in wide range depending on amount of bacilli and host immune response
• WHO classification
  • MB - multibacillary > 5 lesions
    • multi-drug Tx for 1 year
  • PB - paucibacillary 2-5 lesions
    • multi-drug Tx for 6 months
  • single lesion
    • single dose
• Rideley & Jpling classification
  • TT
  • BT
  • BB
  • BL
  • LL
• delay of Dx and Tx leads to long term disability and deformity resulted in stigma and discrimination

Buruli ulcer

• Mycobacterium ulcerans
• 75% of worldwide patients are in Ivory Coast, Ghana and Benin
  • rarely found in Japan and Australia (esp. in Victoria)
• transmission route unknown
  • patients are often in proximity of stagnant water body
  • reservoir - snails, fish, water insects, aquatic plants, koala & opposum in Australia
• undermined wound edges, thick necrotic tissue, pain is liminited
• 3 months course

1. subcutaneous nodules
2. plaque
3. edema - develops pain
4. ulcer

• diagnosis - Ziehl-Neelsen stain and culture of ulcer base
• DDx - panniculitis, pyoderma gangreosum
• lipid toxin produced and secreted by M. ulcerans is pathogenetic
  • highly hydrophobic
  • M. ulcerans itself is not pathogenetic
• WHO treatment category
  • I lesions<5cm - 8 weeks antibiotics
  • II lesions 5-15cm - 4 weeks antibiotics -> surgery -> 4 weeks
  • III lesions >15cm

Lesishmaniasis

• Leischmania spp. > 20 species
  • intracellular protozoa
• transmitted by sandfly
• 3 clinical types
  • cutaneous
  • mucocutaneous
  • visceral (Kala-Azar)

Onchoceriasis

• Onchocera volvulus
• transmitted by blackfly
• mass drug administration in Central Africa region is dangerous because Loa loa is endemic, which may cause encephalitis by administration of ivermectin

Lyphmatic filariasis

• Wuchereria bancrofti, Brugia malayi, Brugia timori

Yaws

• イチゴ腫，フランベジア
  • 病変がフランボワーズ（ラズベリー）に似ているため
• Treponema pallidum subsp. pertenue
• more common in children
• direct contact transmission
• yellowish, raspberry-like nodule
  • often develop ulceration
• diagnosis
  • treponema pallidum rapid diagnostic test
  • dual path platform (DPP) test of skin swab
• just one dose of azithromycin 30mg/kg or 2 gram for adults is effective
  • resistant to azithromycin is rapidly increasing in yaws

Mycetoma

• syndrome, not a single etiology
• bacterial
  • Actionomadura madurae, Streptomyces somaliensis, Actinomadura pelletieri, Nocardia spp.
    • actinomycetoma
• fungal
  • Madurella mycetomatis, etc.
    • eumaycetoma
  • black dots are seen on lesions, clusters of fungi
• Txs differ depending on

1. medical for 3-6 months
   1. itraconazole
2. surgical bulk reducion
3. medical for 6 months again

• mainly in 20-40 y/o males
• triad

1. painless subcutaneous mass
2. multiple sinuses
3. discharge containing grains

• in earlier stage, painless nodule
  • look like the first stage of buruli ulcer
• can invade deeper tissues and bones, leading to amputation

Tinea imbricata

• Trichophyton concentricum
• rare form or recurrent itchy ringworm (tinea)
• in tropical, esp. remote villages
• terbinafine 4 weeks

Scabies

• Sarcoptes scabiei var. hominis
• ivermectin

Tungiasis (sand flea)

• Tunga penetrans
  • only female tunga invades human skin producing a large ovary

Guinea worm

• almost eliminated
  • human cases only in 4 countries
  • still exists as zoonosis
• Dracunculus medinensis