Infectious Dermatology

Question 1

What’s the diagnosis here? Hint: note that the organisms like to line up at the periphery of vacuoles, like the bulbs on an old-fashioned mirror, or the bulbs on the sign for an old-fashioned movie theatre (“Marquis sign”).

Answer 1

Leishmaniasis

Question 2

What’s the diagnosis? What’s the causative agent?

Answer 2

• Tinea imbricata
• Trichophyton concentricum

*Note: this condition is limited to Polynesia, Melanesia, India, and Central American.

Question 3

What is the most common cause of tinea pedis?

Answer 3

Trichophyton rubrum

*Note: T. rubrum is also the most common cause of tinea manuum.

Question 4

What is the most common location for an id reaction to tinea pedis?

Answer 4

The hands and sides of the fingers

Question 5

What ingredient can be added to KOH to speed the clearing of keratin, without the need for heating?

Answer 5

20-40% DMSO

Question 6

What % KOH is used in KOH fungal preparations?

Answer 6

10-20%

Question 7

What’s the diagnosis in biopsy of the toe from a patient who was recently walking along a beach in a tropical location? Hint: this was caused by a jigger flea.

Answer 7

Tunga penetrans (tungiasis)

Question 8

What’s the diagnosis?

Answer 8

Round worm infection, in this case onchocerciasis

*Note: below is a baby onchocercoma, a “microfilaria”.

Question 9

True or false: CD30+ lymphocytes may be abundant in arthropod bites.

Answer 9

True; many atypical CD30+ lymphocytes may be present in “mature” bug bites