Arthropods

Scabies pathogenesis

Caused by Sarcoptes scabiei; burrow into SC; cause type IV hypersensitivity

Clinical Manifestation of scabies

Intense pruritus esp at night; burrows; Norwegian (crusted) scabies

What is Norwegian (Crusted) scabies)

Hyperkeratotic, highly contagious version found in immunocompromised patients

Sarcoptes scabiei

Classic Scabies

Crusted scabies

Linear burrow to lay eggs in

Complications of scabies

Psychological and sleep distress, secondary bacterial infection (impetigo), persistent pruritus

Demodex

What is demodex

Found normally in hair and sebaceous glands; immunosuppression causes overgrowth

Clinical manifestation of demodicosis

Demodex folliculitis, rosacea and ocular demodicosis

Demodex folliculitis

Rosacea

Ocular demodicosis

What are the suspicion of demodex infestation

Treatment resistant rosacea, folliculitis or chronic blepharitis

What is the pathophysiology of the Black Widow spider

Cause a latrotoxin that cause presynaptic ACh release

Clinical presentation of black widow spider bite

Initially painless bite → Severe muscle cramps, ab rigidity

Brown recluse spider pathogenesis

Has sphingomyelinase D that causes necrosis; found in undisturbed areas

Clinical manifestation of brown recluse spider bite

Painless initial bite → Painful ulceration within hours

Dermonecrotic bite from brown recluse spider

What causes lyme disease

Borellia burgdorferi from Ixodes (blacklegged) tick;

What is the clinical manifestation of lyme disease

Erythema migrans (bulls eye lesion)

Erythema migrans

Ixodes blacklegged tick

Dog tick (dermacentor variabilis)

RMSF pathogenesis

Caused by rickettsia rickettsii from the dog tick

Clinical manifestation of RMSF

Prodromal symptoms → Cutaneous manifestation (macules on wrist and ankle)

Macules on wrist caused by RMSF

Scrub typhus pathogenesis

Caused by orientia tsutsugamsushi in Chiggers (mites)

Chigger

Clinical manifestation of scrub typhus

Eschar

Eschar caused by scrub typhus

Head Lice

Pathogenesis of head lice

Head to head contact; secondary transmission from fomite

Clinical manifestation of head lice

Scalp pruritus, excoriation from scratching

Pubic lice

Pathogenesis of pubic lice

Sexual contact spread

Pubic lice clinical features

Intense pruritus in pubic region; MACULAE CERULAE

Body lice pathogenesis

Primarily on clothing

Body lice diseases

Epidemic typhus, trench fever, relapsing fever

Rove beetle

Pathogenesis of rove beetle

Cause lesionwhen crushed against skin (NOT BITE OR STING)

Clinical sign of rove beetle

Whiplash pattern and kissing lesion

Whiplash pattern

Kissing lesion

Bed bug

Pathogenesis of bed bugs

Attracted to CO2 and feed on blood

Bed bug bite (ALWAYS IN GROUPS OF 3)

Dengue rash

sand fly

Clinical manifestation of Leishmaniasis

Cutaneous ulcer, mucocutaneous lesion destruction, visceral (kala-azar) fever, hepatosplenomegaly, pancytopenia

Lesion of leishmaniasis

Leishmania in WBC